diff --git a/backend/app/api/routes.py b/backend/app/api/routes.py
index dcec10fe..8a6beff6 100644
--- a/backend/app/api/routes.py
+++ b/backend/app/api/routes.py
@@ -91,7 +91,7 @@ async def run_analysis(
                 research_depth=request.research_depth,
                 deep_think_llm=request.deep_think_llm,
                 quick_think_llm=request.quick_think_llm,
-                openai_api_key=request.openai_api_key,
+                openai_api_key=request.openai_api_key or "",  # Pass empty string if None, service handles it
                 openai_base_url=request.openai_base_url,
                 alpha_vantage_api_key=request.alpha_vantage_api_key,
             ))
diff --git a/backend/app/models/schemas.py b/backend/app/models/schemas.py
index 1748351a..76293a25 100644
--- a/backend/app/models/schemas.py
+++ b/backend/app/models/schemas.py
@@ -19,7 +19,7 @@ class AnalysisRequest(BaseModel):
     quick_think_llm: Optional[str] = Field(default="gpt-4o-mini", description="Quick thinking LLM model")
     
     # API Configuration
-    openai_api_key: str = Field(..., description="OpenAI API Key (required)", min_length=10)
+    openai_api_key: Optional[str] = Field(None, description="OpenAI API Key (optional if set on server)", min_length=0)
     openai_base_url: Optional[str] = Field(
         default="https://api.openai.com/v1",
         description="OpenAI API Base URL (optional)"
diff --git a/backend/app/services/trading_service.py b/backend/app/services/trading_service.py
index 20850d96..a3ab9144 100644
--- a/backend/app/services/trading_service.py
+++ b/backend/app/services/trading_service.py
@@ -79,7 +79,12 @@ class TradingService:
             
             try:
                 # Set API keys for this request
-                os.environ["OPENAI_API_KEY"] = openai_api_key
+                if openai_api_key:
+                    os.environ["OPENAI_API_KEY"] = openai_api_key
+                elif not os.environ.get("OPENAI_API_KEY"):
+                    # If no key provided and no env var, this will fail later, but let's log it
+                    logger.warning("No OpenAI API key provided in request or environment")
+
                 if alpha_vantage_api_key:
                     os.environ["ALPHA_VANTAGE_API_KEY"] = alpha_vantage_api_key
                 
@@ -136,10 +141,12 @@ class TradingService:
                 }
                 
             finally:
+                # Clean up environment variables after request
                 # Clean up environment variables after request
                 if original_openai_key is not None:
                     os.environ["OPENAI_API_KEY"] = original_openai_key
-                elif "OPENAI_API_KEY" in os.environ:
+                elif openai_api_key and "OPENAI_API_KEY" in os.environ:
+                    # Only delete if we set it (and there was no original key)
                     del os.environ["OPENAI_API_KEY"]
                     
                 if original_alpha_key is not None:
diff --git a/frontend/components/analysis/AnalysisForm.tsx b/frontend/components/analysis/AnalysisForm.tsx
index 91aaa19c..712b3c70 100644
--- a/frontend/components/analysis/AnalysisForm.tsx
+++ b/frontend/components/analysis/AnalysisForm.tsx
@@ -40,7 +40,7 @@ const formSchema = z.object({
   deep_thinking_agent: z.string().min(1, "請選擇深層思維模型"),
   
   // API Configuration
-  openai_api_key: z.string().min(20, "請輸入有效的 OpenAI API Key"),
+  openai_api_key: z.string().optional().or(z.literal("")),
   openai_base_url: z.string().url("請輸入有效的 URL").optional().or(z.literal("")),
   alpha_vantage_api_key: z.string().optional().or(z.literal("")),
 });
@@ -294,12 +294,12 @@ export function AnalysisForm({ onSubmit, loading = false }: AnalysisFormProps) {
                 name="openai_api_key"
                 render={({ field }) => (
                   <FormItem>
-                    <FormLabel>OpenAI API Key（必填）</FormLabel>
+                    <FormLabel>OpenAI API Key（若伺服器已設定則選填）</FormLabel>
                     <FormControl>
                       <Input type="password" placeholder="sk-..." {...field} />
                     </FormControl>
                     <FormDescription>
-                      您的 OpenAI API Key（用於 LLM 推理）
+                      您的 OpenAI API Key（若未填寫將使用伺服器環境變數）
                     </FormDescription>
                     <FormMessage />
                   </FormItem>