diff --git a/server/src/demo/demo-defaults.ts b/server/src/demo/demo-defaults.ts
index 66bec29..14ba853 100644
--- a/server/src/demo/demo-defaults.ts
+++ b/server/src/demo/demo-defaults.ts
@@ -23,7 +23,7 @@ export const DEMO_SYSTEM_SETTINGS = {
       modelName: 'kimi-k2.6',
       fallbackModelName: 'moonshot-v1-auto',
     },
-    deepseek: { endpoint: 'https://api.deepseek.com/v1', apiKey: '', modelName: 'deepseek-chat', fallbackModelName: '' },
+    deepseek: { endpoint: 'https://api.deepseek.com/v1', apiKey: '', modelName: 'deepseek-v4-flash', fallbackModelName: 'deepseek-v4-pro' },
     openai: { endpoint: 'https://api.openai.com/v1', apiKey: '', modelName: 'gpt-4o', fallbackModelName: '' },
     custom: { endpoint: '', apiKey: '', modelName: '', fallbackModelName: '' },
   },
diff --git a/server/src/settings/settings.service.ts b/server/src/settings/settings.service.ts
index 5a16cdd..4bff2d2 100644
--- a/server/src/settings/settings.service.ts
+++ b/server/src/settings/settings.service.ts
@@ -19,7 +19,7 @@ const DEFAULT_AI_PROVIDERS = {
     modelName: 'kimi-k2.6',
     fallbackModelName: 'moonshot-v1-auto',
   },
-  deepseek: { endpoint: 'https://api.deepseek.com/v1', apiKey: '', modelName: 'deepseek-chat', fallbackModelName: '' },
+  deepseek: { endpoint: 'https://api.deepseek.com/v1', apiKey: '', modelName: 'deepseek-v4-flash', fallbackModelName: 'deepseek-v4-pro' },
   openai: { endpoint: 'https://api.openai.com/v1', apiKey: '', modelName: 'gpt-4o', fallbackModelName: '' },
   custom: { endpoint: '', apiKey: '', modelName: '', fallbackModelName: '' },
 };
@@ -288,6 +288,12 @@ export class SettingsService {
         if (key === 'kimi' && /^kimi-k2(?:-|$)/i.test(provider.fallbackModelName || '')) {
           provider.fallbackModelName = DEFAULT_AI_PROVIDERS.kimi.fallbackModelName;
         }
+        if (key === 'deepseek' && provider.modelName === 'deepseek-chat') {
+          provider.modelName = DEFAULT_AI_PROVIDERS.deepseek.modelName;
+        }
+        if (key === 'deepseek' && provider.fallbackModelName === 'deepseek-reasoner') {
+          provider.fallbackModelName = DEFAULT_AI_PROVIDERS.deepseek.fallbackModelName;
+        }
         return [key, provider];
       }),
     );
diff --git a/src/pages/SystemSettings.tsx b/src/pages/SystemSettings.tsx
index b93f5cb..47d5688 100644
--- a/src/pages/SystemSettings.tsx
+++ b/src/pages/SystemSettings.tsx
@@ -30,6 +30,12 @@ const normalizeSettings = (
       if (key === 'kimi' && /^kimi-k2(?:-|$)/i.test(provider.fallbackModelName || '')) {
         provider.fallbackModelName = DEFAULT_AI_PROVIDERS.kimi.fallbackModelName;
       }
+      if (key === 'deepseek' && provider.modelName === 'deepseek-chat') {
+        provider.modelName = DEFAULT_AI_PROVIDERS.deepseek.modelName;
+      }
+      if (key === 'deepseek' && provider.fallbackModelName === 'deepseek-reasoner') {
+        provider.fallbackModelName = DEFAULT_AI_PROVIDERS.deepseek.fallbackModelName;
+      }
       return [key, provider];
     }),
   );
diff --git a/src/types.ts b/src/types.ts
index 40cb672..d152f66 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -119,7 +119,7 @@ export const DEFAULT_AI_PROVIDERS: Record<string, AiProviderConfig> = {
     modelName: 'kimi-k2.6',
     fallbackModelName: 'moonshot-v1-auto'
   },
-  deepseek: { endpoint: 'https://api.deepseek.com/v1', apiKey: '', modelName: 'deepseek-chat', fallbackModelName: '' },
+  deepseek: { endpoint: 'https://api.deepseek.com/v1', apiKey: '', modelName: 'deepseek-v4-flash', fallbackModelName: 'deepseek-v4-pro' },
   openai: { endpoint: 'https://api.openai.com/v1', apiKey: '', modelName: 'gpt-4o', fallbackModelName: '' },
   custom: { endpoint: '', apiKey: '', modelName: '', fallbackModelName: '' }
 };