diff --git a/backend/.env b/backend/.env
new file mode 100644
index 00000000..6720a98a
--- /dev/null
+++ b/backend/.env
@@ -0,0 +1,2 @@
+PRIMARY_API_KEY=你的主密钥
+FALLBACK_API_KEY=你的备用密钥
diff --git a/backend/config/models.js b/backend/config/models.js
index 6ef24385..03d8eb07 100644
--- a/backend/config/models.js
+++ b/backend/config/models.js
@@ -1,19 +1,21 @@
-// 模型路由配置（统一走云雾API中转）
-const YUNWU_API_URL = 'https://api.deepseek.com/v1/chat/completions';
-const YUNWU_KEY = process.env.YUNWU_API_KEY;
+// 模型路由配置（支持主备API自动切换）
+const PRIMARY_API_KEY = process.env.PRIMARY_API_KEY;
+const FALLBACK_API_KEY = process.env.FALLBACK_API_KEY;
 
 const MODELS = {
   deepseek: {
     name: 'DeepSeek Chat',
-    apiUrl: YUNWU_API_URL,
-    apiKey: YUNWU_KEY,
+    apiUrl: 'https://api.deepseek.com/v1/chat/completions',
+    primaryApiKey: PRIMARY_API_KEY,
+    fallbackApiKey: FALLBACK_API_KEY,
     model: 'deepseek-chat',
     maxTokens: 4096
   },
   gpt4o_mini: {
     name: 'GPT-4o-mini',
-    apiUrl: YUNWU_API_URL,
-    apiKey: YUNWU_KEY,
+    apiUrl: 'https://api.deepseek.com/v1/chat/completions',
+    primaryApiKey: PRIMARY_API_KEY,
+    fallbackApiKey: FALLBACK_API_KEY,
     model: 'gpt-4o-mini',
     maxTokens: 4096
   }
diff --git a/backend/config/models.js.bak b/backend/config/models.js.bak
new file mode 100644
index 00000000..6ef24385
--- /dev/null
+++ b/backend/config/models.js.bak
@@ -0,0 +1,27 @@
+// 模型路由配置（统一走云雾API中转）
+const YUNWU_API_URL = 'https://api.deepseek.com/v1/chat/completions';
+const YUNWU_KEY = process.env.YUNWU_API_KEY;
+
+const MODELS = {
+  deepseek: {
+    name: 'DeepSeek Chat',
+    apiUrl: YUNWU_API_URL,
+    apiKey: YUNWU_KEY,
+    model: 'deepseek-chat',
+    maxTokens: 4096
+  },
+  gpt4o_mini: {
+    name: 'GPT-4o-mini',
+    apiUrl: YUNWU_API_URL,
+    apiKey: YUNWU_KEY,
+    model: 'gpt-4o-mini',
+    maxTokens: 4096
+  }
+};
+
+const DEFAULT_MODEL = 'deepseek';
+
+module.exports = {
+  MODELS,
+  DEFAULT_MODEL
+};
diff --git a/backend/routes/router.js b/backend/routes/router.js
index 2189677c..1b759f8a 100644
--- a/backend/routes/router.js
+++ b/backend/routes/router.js
@@ -6,12 +6,71 @@ const { MODELS, DEFAULT_MODEL } = require('../config/models');
 router.get('/test', (req, res) => {
   res.json({
     status: 'ok',
-    message: '模型路由正常 ❤️',
+    message: '模型路由正常 ❤️ (支持主备自动切换)',
     available_models: Object.keys(MODELS),
     default_model: DEFAULT_MODEL
   });
 });
 
+// 带 fallback 的 API 调用函数
+async function callAPIWithFallback(model, message) {
+  // 第一次尝试：主密钥
+  try {
+    console.log(`[API] 尝试使用主密钥调用 ${model.name}`);
+    const response = await axios.post(
+      model.apiUrl,
+      {
+        model: model.model,
+        messages: [{ role: 'user', content: message }],
+        max_tokens: model.maxTokens
+      },
+      {
+        headers: {
+          'Authorization': 'Bearer ' + model.primaryApiKey,
+          'Content-Type': 'application/json'
+        }
+      }
+    );
+    return { success: true, data: response.data };
+  } catch (primaryErr) {
+    // 判断是否需要 fallback（余额不足/超时/401/403）
+    const shouldFallback = 
+      primaryErr.response?.status === 401 ||
+      primaryErr.response?.status === 403 ||
+      primaryErr.response?.data?.error?.type === 'insufficient_quota' ||
+      primaryErr.code === 'ECONNABORTED' ||
+      primaryErr.message.includes('timeout');
+
+    if (!shouldFallback || !model.fallbackApiKey) {
+      // 不需要 fallback 或没有备用密钥，直接抛出错误
+      throw primaryErr;
+    }
+
+    // 需要 fallback，尝试备用密钥
+    console.log(`[API Fallback] 从主密钥切换到备用密钥 (${model.name})`);
+    try {
+      const fallbackResponse = await axios.post(
+        model.apiUrl,
+        {
+          model: model.model,
+          messages: [{ role: 'user', content: message }],
+          max_tokens: model.maxTokens
+        },
+        {
+          headers: {
+            'Authorization': 'Bearer ' + model.fallbackApiKey,
+            'Content-Type': 'application/json'
+          }
+        }
+      );
+      return { success: true, data: fallbackResponse.data, fallback: true };
+    } catch (fallbackErr) {
+      // 备用也失败了，抛出备用错误
+      throw fallbackErr;
+    }
+  }
+}
+
 router.post('/chat', async (req, res) => {
   try {
     const { message, model_name } = req.body;
@@ -21,33 +80,22 @@ router.post('/chat', async (req, res) => {
       return res.status(400).json({ error: '未知模型: ' + model_name });
     }
 
-    if (!model.apiKey) {
+    if (!model.primaryApiKey) {
       return res.status(503).json({ 
-        error: '模型 ' + model.name + ' 的 API Key 尚未配置', 
-        hint: '请检查 .env 文件中的 YUNWU_API_KEY' 
+        error: '模型 ' + model.name + ' 的主 API Key 尚未配置', 
+        hint: '请检查 .env 文件中的 PRIMARY_API_KEY' 
       });
     }
 
-    const response = await axios.post(
-      model.apiUrl,
-      {
-        model: model.model,
-        messages: [{ role: 'user', content: message }],
-        max_tokens: model.maxTokens
-      },
-      {
-        headers: {
-          'Authorization': 'Bearer ' + model.apiKey,
-          'Content-Type': 'application/json'
-        }
-      }
-    );
-
+    const result = await callAPIWithFallback(model, message);
+    
     res.json({
       model: model.name,
-      reply: response.data.choices[0].message.content
+      reply: result.data.choices[0].message.content,
+      fallback_used: result.fallback || false
     });
   } catch (err) {
+    console.error('[API Error]', err.message);
     res.status(500).json({
       error: err.message,
       detail: err.response ? err.response.data : null
diff --git a/backend/routes/router.js.bak b/backend/routes/router.js.bak
new file mode 100644
index 00000000..2189677c
--- /dev/null
+++ b/backend/routes/router.js.bak
@@ -0,0 +1,58 @@
+const express = require('express');
+const axios = require('axios');
+const router = express.Router();
+const { MODELS, DEFAULT_MODEL } = require('../config/models');
+
+router.get('/test', (req, res) => {
+  res.json({
+    status: 'ok',
+    message: '模型路由正常 ❤️',
+    available_models: Object.keys(MODELS),
+    default_model: DEFAULT_MODEL
+  });
+});
+
+router.post('/chat', async (req, res) => {
+  try {
+    const { message, model_name } = req.body;
+    const model = MODELS[model_name || DEFAULT_MODEL];
+
+    if (!model) {
+      return res.status(400).json({ error: '未知模型: ' + model_name });
+    }
+
+    if (!model.apiKey) {
+      return res.status(503).json({ 
+        error: '模型 ' + model.name + ' 的 API Key 尚未配置', 
+        hint: '请检查 .env 文件中的 YUNWU_API_KEY' 
+      });
+    }
+
+    const response = await axios.post(
+      model.apiUrl,
+      {
+        model: model.model,
+        messages: [{ role: 'user', content: message }],
+        max_tokens: model.maxTokens
+      },
+      {
+        headers: {
+          'Authorization': 'Bearer ' + model.apiKey,
+          'Content-Type': 'application/json'
+        }
+      }
+    );
+
+    res.json({
+      model: model.name,
+      reply: response.data.choices[0].message.content
+    });
+  } catch (err) {
+    res.status(500).json({
+      error: err.message,
+      detail: err.response ? err.response.data : null
+    });
+  }
+});
+
+module.exports = router;