diff --git a/backend/main.py b/backend/main.py
new file mode 100644
index 0000000..f67c295
--- /dev/null
+++ b/backend/main.py
@@ -0,0 +1,74 @@
+"""
+NAC 一键上链系统 - 主入口
+版本: 3.0 (真实注册/登录 + 多语言 + 17步工作流)
+"""
+import os
+import logging
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.staticfiles import StaticFiles
+from fastapi.responses import FileResponse
+# 路由模块
+from routers import assets, onboarding, node
+from routers.users import router as users_router
+
+# 日志配置
+logging.basicConfig(
+    level=logging.INFO,
+    format='%(asctime)s [%(name)s] %(levelname)s: %(message)s',
+    handlers=[
+        logging.StreamHandler(),
+        logging.FileHandler('/opt/nac/onboarding/logs/app.log', encoding='utf-8')
+    ]
+)
+logger = logging.getLogger('nac-onboarding')
+
+app = FastAPI(
+    title='NAC 一键资产上链系统',
+    description='基于NAC公链的RWA资产上链平台 - 17步完整工作流',
+    version='3.0.0',
+    docs_url='/api/docs',
+    redoc_url='/api/redoc'
+)
+
+# CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=['*'],
+    allow_credentials=True,
+    allow_methods=['*'],
+    allow_headers=['*'],
+)
+
+# API路由注册
+app.include_router(users_router, prefix='/api/users', tags=['用户认证'])
+app.include_router(assets.router, prefix='/api/assets', tags=['资产管理'])
+app.include_router(onboarding.router, prefix='/api/onboarding', tags=['上链流程'])
+app.include_router(node.router, prefix='/api/node', tags=['节点状态'])
+
+@app.get('/api/health')
+async def health():
+    from database import db
+    try:
+        await db.command('ping')
+        mongo_status = 'connected'
+    except Exception:
+        mongo_status = 'disconnected'
+    return {
+        'status': 'ok',
+        'version': '3.0.0',
+        'mongo': mongo_status,
+        'protocol': 'NAC-Lens/4.0',
+        'auth': 'local-jwt'
+    }
+
+# 前端静态文件服务
+frontend_dir = '/opt/nac/onboarding/frontend'
+if os.path.exists(frontend_dir):
+    app.mount('/assets', StaticFiles(directory=f'{frontend_dir}/assets'), name='assets')
+    @app.get('/{full_path:path}')
+    async def serve_frontend(full_path: str):
+        index = f'{frontend_dir}/index.html'
+        if os.path.exists(index):
+            return FileResponse(index)
+        return {'error': '前端未构建'}