diff --git a/tests/unit/test_api_settings.py b/tests/unit/test_api_settings.py
index f7689fd31..1b4c776f0 100755
--- a/tests/unit/test_api_settings.py
+++ b/tests/unit/test_api_settings.py
@@ -12,11 +12,23 @@ from packages.config.base import SharedSettings, get_cached_settings, reload_set
 def _reset_cache():
     """每个测试前清空配置缓存，避免单例污染."""
     reload_settings_cache()
+    # 保存关键环境变量（避免其他测试模块的全局污染）
+    _saved_env = {}
+    for key in ["JWT_SECRET_KEY", "DATABASE_URL", "USE_IN_MEMORY_DB", "APP_ENV"]:
+        _saved_env[key] = os.environ.get(key)
     # 设置必要的环境变量，避免 JWT 校验失败
     os.environ["JWT_SECRET_KEY"] = "test-secret-key-for-unit-tests-only-12345"
+    # 清除可能被其他模块污染的变量，确保默认值测试准确
+    for key in ["DATABASE_URL", "APP_ENV"]:
+        os.environ.pop(key, None)
     yield
     reload_settings_cache()
-    os.environ.pop("JWT_SECRET_KEY", None)
+    # 恢复所有保存的环境变量，避免污染其他测试模块
+    for key, val in _saved_env.items():
+        if val is None:
+            os.environ.pop(key, None)
+        else:
+            os.environ[key] = val
 
 
 class TestSharedSettingsDefaults: