diff --git a/main.py b/main.py
index 6704193..0346ec8 100644
--- a/main.py
+++ b/main.py
@@ -1,9 +1,8 @@
 import logging
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
-from config import DATABASE_CONFIG, JWT_CONFIG, LOGGING_CONFIG, SYSTEM_ADMIN_CONFIG
-from sqlalchemy.ext.asyncio import create_async_engine
-from services.init_db import init_db
+from config import JWT_CONFIG, LOGGING_CONFIG, SYSTEM_ADMIN_CONFIG
+from services.db import create_db_engine, init_db, close_db_connection
 from routes.auth import auth_router
 from routes.users import users_router
 
@@ -22,20 +21,20 @@ app = FastAPI(
     version="1.0.0"
 )
 
-# 创建数据库引擎
-engine = create_async_engine(
-    f"mysql+asyncmy://{DATABASE_CONFIG['user']}:{DATABASE_CONFIG['password']}@"
-    f"{DATABASE_CONFIG['host']}:{DATABASE_CONFIG['port']}/{DATABASE_CONFIG['database']}",
-    echo=True
-)
-
-# 初始化数据库
+# 数据库初始化
 @app.on_event("startup")
 async def startup_event():
     logger.info("Initializing database...")
+    engine = create_db_engine()
     await init_db(engine)
     logger.info("Database initialized successfully")
 
+@app.on_event("shutdown")
+async def shutdown_event():
+    logger.info("Closing database connections...")
+    await close_db_connection()
+    logger.info("Database connections closed")
+
 # 注册路由
 app.include_router(auth_router, prefix="/api/auth", tags=["auth"])
 app.include_router(users_router, prefix="/api/users", tags=["users"])
diff --git a/services/db.py b/services/db.py
new file mode 100644
index 0000000..3f7c6cb
--- /dev/null
+++ b/services/db.py
@@ -0,0 +1,67 @@
+from sqlalchemy.ext.asyncio import AsyncEngine, create_async_engine, AsyncSession
+from sqlalchemy.orm import sessionmaker
+from ..models.user import Base, User, UserRole
+from sqlalchemy import select
+from contextlib import asynccontextmanager
+from config import SYSTEM_ADMIN_CONFIG, DATABASE_CONFIG
+from services.auth import get_password_hash
+from typing import AsyncGenerator
+
+# 全局数据库引擎实例
+_engine: AsyncEngine | None = None
+
+def create_db_engine() -> AsyncEngine:
+    """创建数据库引擎"""
+    return create_async_engine(
+        f"mysql+asyncmy://{DATABASE_CONFIG['user']}:{DATABASE_CONFIG['password']}@"
+        f"{DATABASE_CONFIG['host']}:{DATABASE_CONFIG['port']}/{DATABASE_CONFIG['database']}",
+        echo=True
+    )
+
+def get_db_engine() -> AsyncEngine:
+    """获取全局数据库引擎实例"""
+    if _engine is None:
+        raise RuntimeError("Database engine not initialized")
+    return _engine
+
+@asynccontextmanager
+async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
+    """获取数据库会话"""
+    async with AsyncSession(get_db_engine()) as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise
+
+async def init_db(engine: AsyncEngine):
+    """初始化数据库"""
+    global _engine
+    _engine = engine
+    
+    async with engine.begin() as conn:
+        # 创建所有表
+        await conn.run_sync(Base.metadata.create_all)
+
+        # 检查系统管理员是否存在
+        result = await conn.execute(
+            select(User).where(User.role == UserRole.SYSTEM_ADMIN)
+        )
+        if not result.scalars().first():
+            # 创建默认系统管理员
+            admin = User(
+                username=SYSTEM_ADMIN_CONFIG['username'],
+                password=get_password_hash(SYSTEM_ADMIN_CONFIG['password']),
+                role=UserRole.SYSTEM_ADMIN,
+                description=SYSTEM_ADMIN_CONFIG['description']
+            )
+            conn.add(admin)
+            await conn.commit()
+
+async def close_db_connection():
+    """关闭数据库连接"""
+    global _engine
+    if _engine is not None:
+        await _engine.dispose()
+        _engine = None
diff --git a/services/init_db.py b/services/init_db.py
deleted file mode 100644
index 23c8125..0000000
--- a/services/init_db.py
+++ /dev/null
@@ -1,26 +0,0 @@
-from sqlalchemy.ext.asyncio import AsyncEngine
-from ..models.user import Base, User, UserRole
-from sqlalchemy import select
-from config import SYSTEM_ADMIN_CONFIG
-from services.auth import get_password_hash
-
-async def init_db(engine: AsyncEngine):
-    """初始化数据库"""
-    async with engine.begin() as conn:
-        # 创建所有表
-        await conn.run_sync(Base.metadata.create_all)
-
-        # 检查系统管理员是否存在
-        result = await conn.execute(
-            select(User).where(User.role == UserRole.SYSTEM_ADMIN)
-        )
-        if not result.scalars().first():
-            # 创建默认系统管理员
-            admin = User(
-                username=SYSTEM_ADMIN_CONFIG['username'],
-                password=get_password_hash(SYSTEM_ADMIN_CONFIG['password']),
-                role=UserRole.SYSTEM_ADMIN,
-                description=SYSTEM_ADMIN_CONFIG['description']
-            )
-            conn.add(admin)
-            await conn.commit()