diff --git a/packages/domain/quota.py b/packages/domain/quota.py
new file mode 100644
index 000000000..aa20811f8
--- /dev/null
+++ b/packages/domain/quota.py
@@ -0,0 +1,178 @@
+"""
+配额检查服务
+用于检查工作空间是否超出配额限制
+"""
+from typing import Optional
+
+
+class QuotaChecker:
+    """配额检查器"""
+    
+    def __init__(
+        self,
+        workspace_repository,
+        project_repository,
+    ):
+        self.workspace_repository = workspace_repository
+        self.project_repository = project_repository
+    
+    def check_can_create_project(
+        self,
+        workspace_id: str,
+    ) -> tuple[bool, Optional[str]]:
+        """
+        检查是否可以创建项目
+        
+        Args:
+            workspace_id: 工作空间 ID
+        
+        Returns:
+            (是否可以, 错误信息)
+        """
+        workspace = self.workspace_repository.find_by_id(workspace_id)
+        if not workspace:
+            return False, "Workspace not found"
+        
+        # 获取当前项目数量
+        current_count = self.project_repository.count_by_workspace(workspace_id)
+        
+        # 检查是否超出配额（999999 表示无限）
+        if workspace.max_projects != 999999 and current_count >= workspace.max_projects:
+            return False, f"Project limit reached ({workspace.max_projects}). Upgrade your plan to create more projects."
+        
+        return True, None
+    
+    def check_storage_available(
+        self,
+        workspace_id: str,
+        additional_gb: float,
+    ) -> tuple[bool, Optional[str]]:
+        """
+        检查存储空间是否足够
+        
+        Args:
+            workspace_id: 工作空间 ID
+            additional_gb: 需要的额外存储空间（GB）
+        
+        Returns:
+            (是否可以, 错误信息)
+        """
+        workspace = self.workspace_repository.find_by_id(workspace_id)
+        if not workspace:
+            return False, "Workspace not found"
+        
+        # 检查存储空间
+        new_usage = workspace.used_storage_gb + additional_gb
+        
+        if new_usage > workspace.max_storage_gb:
+            remaining = workspace.max_storage_gb - workspace.used_storage_gb
+            return False, f"Storage limit exceeded. Available: {remaining:.2f}GB, Required: {additional_gb:.2f}GB. Upgrade your plan for more storage."
+        
+        return True, None
+    
+    def get_quota_status(self, workspace_id: str) -> dict:
+        """
+        获取配额使用状态
+        
+        Args:
+            workspace_id: 工作空间 ID
+        
+        Returns:
+            配额状态信息
+        """
+        workspace = self.workspace_repository.find_by_id(workspace_id)
+        if not workspace:
+            return None
+        
+        # 获取项目数量
+        project_count = self.project_repository.count_by_workspace(workspace_id)
+        
+        # 计算使用率
+        project_usage_percent = (
+            (project_count / workspace.max_projects * 100)
+            if workspace.max_projects != 999999
+            else 0  # 无限制
+        )
+        
+        storage_usage_percent = (
+            (workspace.used_storage_gb / workspace.max_storage_gb * 100)
+            if workspace.max_storage_gb > 0
+            else 0
+        )
+        
+        return {
+            "workspace_id": workspace.id,
+            "subscription_plan": workspace.subscription_plan,
+            "projects": {
+                "used": project_count,
+                "limit": workspace.max_projects,
+                "unlimited": workspace.max_projects == 999999,
+                "usage_percent": project_usage_percent,
+            },
+            "storage": {
+                "used_gb": workspace.used_storage_gb,
+                "limit_gb": workspace.max_storage_gb,
+                "remaining_gb": workspace.max_storage_gb - workspace.used_storage_gb,
+                "usage_percent": storage_usage_percent,
+            },
+        }
+    
+    def update_storage_usage(
+        self,
+        workspace_id: str,
+        delta_gb: float,
+    ) -> tuple[bool, Optional[str]]:
+        """
+        更新存储使用量
+        
+        Args:
+            workspace_id: 工作空间 ID
+            delta_gb: 变化量（正数为增加，负数为减少）
+        
+        Returns:
+            (是否成功, 错误信息)
+        """
+        workspace = self.workspace_repository.find_by_id(workspace_id)
+        if not workspace:
+            return False, "Workspace not found"
+        
+        # 更新使用量
+        new_usage = workspace.used_storage_gb + delta_gb
+        
+        # 不能为负数
+        if new_usage < 0:
+            new_usage = 0
+        
+        workspace.used_storage_gb = new_usage
+        self.workspace_repository.save(workspace)
+        
+        return True, None
+
+
+class QuotaWarningLevel:
+    """配额警告级别"""
+    
+    NORMAL = "normal"  # <80%
+    WARNING = "warning"  # 80-90%
+    CRITICAL = "critical"  # 90-100%
+    EXCEEDED = "exceeded"  # >100%
+
+
+def get_warning_level(usage_percent: float) -> str:
+    """
+    根据使用率获取警告级别
+    
+    Args:
+        usage_percent: 使用率（0-100）
+    
+    Returns:
+        警告级别
+    """
+    if usage_percent >= 100:
+        return QuotaWarningLevel.EXCEEDED
+    elif usage_percent >= 90:
+        return QuotaWarningLevel.CRITICAL
+    elif usage_percent >= 80:
+        return QuotaWarningLevel.WARNING
+    else:
+        return QuotaWarningLevel.NORMAL
diff --git a/packages/ports/project_repository.py b/packages/ports/project_repository.py
index eae76ed99..fc60b8452 100644
--- a/packages/ports/project_repository.py
+++ b/packages/ports/project_repository.py
@@ -1,13 +1,30 @@
-from __future__ import annotations
-
-from typing import Protocol
-
-from packages.domain import Project
+"""
+Project 仓储接口
+"""
+from abc import ABC, abstractmethod
+from typing import Optional
+from packages.domain.entities import Project
 
 
-class ProjectRepository(Protocol):
-    def list_by_workspace(self, workspace_id: str) -> list[Project]:
-        """List projects for a workspace."""
-
-    def create(self, project: Project) -> Project:
-        """Persist a project and return it."""
+class ProjectRepository(ABC):
+    """Project 仓储接口"""
+    
+    @abstractmethod
+    def save(self, project: Project) -> None:
+        """保存项目"""
+        pass
+    
+    @abstractmethod
+    def find_by_id(self, project_id: str) -> Optional[Project]:
+        """根据 ID 查找项目"""
+        pass
+    
+    @abstractmethod
+    def count_by_workspace(self, workspace_id: str) -> int:
+        """统计工作空间的项目数量"""
+        pass
+    
+    @abstractmethod
+    def delete(self, project_id: str) -> bool:
+        """删除项目"""
+        pass
diff --git a/tests/unit/test_quota.py b/tests/unit/test_quota.py
new file mode 100644
index 000000000..41650eaac
--- /dev/null
+++ b/tests/unit/test_quota.py
@@ -0,0 +1,287 @@
+"""
+配额检查服务测试
+"""
+import pytest
+from unittest.mock import Mock
+from packages.domain.quota import (
+    QuotaChecker,
+    QuotaWarningLevel,
+    get_warning_level,
+)
+from packages.domain.entities import Workspace
+
+
+class TestQuotaChecker:
+    """配额检查器测试"""
+    
+    @pytest.fixture
+    def mock_workspace_repo(self):
+        repo = Mock()
+        repo.find_by_id = Mock(return_value=None)
+        repo.save = Mock()
+        return repo
+    
+    @pytest.fixture
+    def mock_project_repo(self):
+        repo = Mock()
+        repo.count_by_workspace = Mock(return_value=0)
+        return repo
+    
+    @pytest.fixture
+    def checker(self, mock_workspace_repo, mock_project_repo):
+        return QuotaChecker(
+            workspace_repository=mock_workspace_repo,
+            project_repository=mock_project_repo,
+        )
+    
+    def test_check_can_create_project_within_limit(
+        self,
+        checker,
+        mock_workspace_repo,
+        mock_project_repo,
+    ):
+        """测试在配额内可以创建项目"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="free",
+            max_projects=3,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        mock_project_repo.count_by_workspace.return_value = 2
+        
+        can_create, error = checker.check_can_create_project("workspace-123")
+        
+        assert can_create is True
+        assert error is None
+    
+    def test_check_can_create_project_at_limit(
+        self,
+        checker,
+        mock_workspace_repo,
+        mock_project_repo,
+    ):
+        """测试达到配额限制"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="free",
+            max_projects=3,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        mock_project_repo.count_by_workspace.return_value = 3
+        
+        can_create, error = checker.check_can_create_project("workspace-123")
+        
+        assert can_create is False
+        assert "Project limit reached" in error
+    
+    def test_check_can_create_project_unlimited(
+        self,
+        checker,
+        mock_workspace_repo,
+        mock_project_repo,
+    ):
+        """测试无限制计划"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="pro",
+            max_projects=999999,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        mock_project_repo.count_by_workspace.return_value=1000
+        
+        can_create, error = checker.check_can_create_project("workspace-123")
+        
+        assert can_create is True
+        assert error is None
+    
+    def test_check_storage_available_within_limit(
+        self,
+        checker,
+        mock_workspace_repo,
+    ):
+        """测试存储在配额内"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="free",
+            max_storage_gb=10,
+            used_storage_gb=5.0,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        
+        can_store, error = checker.check_storage_available("workspace-123", 3.0)
+        
+        assert can_store is True
+        assert error is None
+    
+    def test_check_storage_available_exceeded(
+        self,
+        checker,
+        mock_workspace_repo,
+    ):
+        """测试存储超出配额"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="free",
+            max_storage_gb=10,
+            used_storage_gb=8.0,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        
+        can_store, error = checker.check_storage_available("workspace-123", 3.0)
+        
+        assert can_store is False
+        assert "Storage limit exceeded" in error
+    
+    def test_get_quota_status(
+        self,
+        checker,
+        mock_workspace_repo,
+        mock_project_repo,
+    ):
+        """测试获取配额状态"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="free",
+            max_projects=3,
+            max_storage_gb=10,
+            used_storage_gb=7.5,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        mock_project_repo.count_by_workspace.return_value = 2
+        
+        status = checker.get_quota_status("workspace-123")
+        
+        assert status is not None
+        assert status["workspace_id"] == "workspace-123"
+        assert status["subscription_plan"] == "free"
+        assert status["projects"]["used"] == 2
+        assert status["projects"]["limit"] == 3
+        assert status["projects"]["usage_percent"] == pytest.approx(66.67, rel=0.1)
+        assert status["storage"]["used_gb"] == 7.5
+        assert status["storage"]["limit_gb"] == 10
+        assert status["storage"]["remaining_gb"] == 2.5
+        assert status["storage"]["usage_percent"] == 75.0
+    
+    def test_get_quota_status_unlimited(
+        self,
+        checker,
+        mock_workspace_repo,
+        mock_project_repo,
+    ):
+        """测试无限制配额状态"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            subscription_plan="pro",
+            max_projects=999999,
+            max_storage_gb=100,
+            used_storage_gb=50.0,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        mock_project_repo.count_by_workspace.return_value = 1000
+        
+        status = checker.get_quota_status("workspace-123")
+        
+        assert status["projects"]["unlimited"] is True
+        assert status["projects"]["usage_percent"] == 0
+    
+    def test_update_storage_usage_increase(
+        self,
+        checker,
+        mock_workspace_repo,
+    ):
+        """测试增加存储使用量"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            max_storage_gb=10,
+            used_storage_gb=5.0,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        
+        success, error = checker.update_storage_usage("workspace-123", 2.5)
+        
+        assert success is True
+        assert error is None
+        assert workspace.used_storage_gb == 7.5
+        mock_workspace_repo.save.assert_called_once()
+    
+    def test_update_storage_usage_decrease(
+        self,
+        checker,
+        mock_workspace_repo,
+    ):
+        """测试减少存储使用量"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            max_storage_gb=10,
+            used_storage_gb=5.0,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        
+        success, error = checker.update_storage_usage("workspace-123", -2.0)
+        
+        assert success is True
+        assert workspace.used_storage_gb == 3.0
+    
+    def test_update_storage_usage_prevent_negative(
+        self,
+        checker,
+        mock_workspace_repo,
+    ):
+        """测试防止负数存储"""
+        workspace = Workspace(
+            id="workspace-123",
+            name="Test",
+            owner_user_id="owner-id",
+            max_storage_gb=10,
+            used_storage_gb=2.0,
+        )
+        mock_workspace_repo.find_by_id.return_value = workspace
+        
+        success, error = checker.update_storage_usage("workspace-123", -5.0)
+        
+        assert success is True
+        assert workspace.used_storage_gb == 0.0
+
+
+class TestWarningLevel:
+    """警告级别测试"""
+    
+    def test_get_warning_level_normal(self):
+        """测试正常级别"""
+        assert get_warning_level(50.0) == QuotaWarningLevel.NORMAL
+        assert get_warning_level(79.9) == QuotaWarningLevel.NORMAL
+    
+    def test_get_warning_level_warning(self):
+        """测试警告级别"""
+        assert get_warning_level(80.0) == QuotaWarningLevel.WARNING
+        assert get_warning_level(85.0) == QuotaWarningLevel.WARNING
+        assert get_warning_level(89.9) == QuotaWarningLevel.WARNING
+    
+    def test_get_warning_level_critical(self):
+        """测试严重级别"""
+        assert get_warning_level(90.0) == QuotaWarningLevel.CRITICAL
+        assert get_warning_level(95.0) == QuotaWarningLevel.CRITICAL
+        assert get_warning_level(99.9) == QuotaWarningLevel.CRITICAL
+    
+    def test_get_warning_level_exceeded(self):
+        """测试超出级别"""
+        assert get_warning_level(100.0) == QuotaWarningLevel.EXCEEDED
+        assert get_warning_level(105.0) == QuotaWarningLevel.EXCEEDED