diff --git a/blueprints/api.py b/blueprints/api.py
index 173e5f2..6815d91 100644
--- a/blueprints/api.py
+++ b/blueprints/api.py
@@ -91,7 +91,7 @@ def generate():
         if image_data:
             payload["image"] = [img.split(',', 1)[1] if ',' in img else img for img in image_data]
             
-        if model_value == "nano-banana-2" and data.get('size'):
+        if model_value in ("nano-banana-2", "gemini-3.1-flash-image-preview") and data.get('size'):
             payload["image_size"] = data.get('size')
 
         # 5. 启动异步生图任务
diff --git a/static/js/main.js b/static/js/main.js
index 9ed8418..f0dae56 100644
--- a/static/js/main.js
+++ b/static/js/main.js
@@ -458,7 +458,8 @@ document.addEventListener('paste', (e) => {
 });
 
 document.getElementById('modelSelect').onchange = (e) => {
-    document.getElementById('sizeGroup').classList.toggle('hidden', e.target.value !== 'nano-banana-2');
+    const sizeModels = ['nano-banana-2', 'gemini-3.1-flash-image-preview'];
+    document.getElementById('sizeGroup').classList.toggle('hidden', !sizeModels.includes(e.target.value));
     updateCostPreview(); // 切换模型时更新计费预览
 };