diff --git a/backend/app/core/deps.py b/backend/app/core/deps.py
index b7140a2..eece509 100644
--- a/backend/app/core/deps.py
+++ b/backend/app/core/deps.py
@@ -6,7 +6,7 @@ from app.config import settings
 
 # 处理 sqlite 协议兼容
 db_url = settings.DATABASE_URL
-if db_url.startswith("sqlite"):
+if db_url.startswith("sqlite://"):
     db_url = db_url.replace("sqlite://", "sqlite+aiosqlite://")
 
 engine = create_async_engine(db_url, echo=False, pool_pre_ping=True)
diff --git a/backend/tests/test_deps_import.py b/backend/tests/test_deps_import.py
index 7d4741b..6be367e 100644
--- a/backend/tests/test_deps_import.py
+++ b/backend/tests/test_deps_import.py
@@ -1,10 +1,48 @@
 """Regression coverage for application dependency module imports."""
 
+import importlib
+import sys
 from pathlib import Path
 
+import pytest
+
 
 def test_dependency_module_compiles():
     """Database initialization dependencies remain valid Python syntax."""
     module_path = Path(__file__).parents[1] / "app" / "core" / "deps.py"
 
     compile(module_path.read_text(encoding="utf-8"), str(module_path), "exec")
+
+
+@pytest.mark.parametrize(
+    ("database_url", "expected_url"),
+    [
+        ("sqlite:///./pingwatch.db", "sqlite+aiosqlite:///./pingwatch.db"),
+        (
+            "sqlite+aiosqlite:///./pingwatch.db",
+            "sqlite+aiosqlite:///./pingwatch.db",
+        ),
+    ],
+)
+def test_dependency_module_normalizes_sqlite_url_once(
+    monkeypatch, database_url, expected_url
+):
+    """Plain SQLite URLs gain the async driver without duplicating an existing one."""
+    monkeypatch.setenv("DATABASE_URL", database_url)
+    sys.modules.pop("app.core.deps", None)
+    sys.modules.pop("app.config", None)
+
+    deps = importlib.import_module("app.core.deps")
+
+    assert str(deps.engine.url) == expected_url
+
+
+def test_dependency_module_initializes_with_default_sqlite_url(monkeypatch):
+    """The default database setting can initialize the asynchronous dependency."""
+    monkeypatch.delenv("DATABASE_URL", raising=False)
+    sys.modules.pop("app.core.deps", None)
+    sys.modules.pop("app.config", None)
+
+    deps = importlib.import_module("app.core.deps")
+
+    assert str(deps.engine.url) == "sqlite+aiosqlite:///./pingwatch.db"