diff --git a/frontend/mobile-app/lib/features/contract_signing/presentation/widgets/signature_pad.dart b/frontend/mobile-app/lib/features/contract_signing/presentation/widgets/signature_pad.dart
index a033c17a..2624d9dd 100644
--- a/frontend/mobile-app/lib/features/contract_signing/presentation/widgets/signature_pad.dart
+++ b/frontend/mobile-app/lib/features/contract_signing/presentation/widgets/signature_pad.dart
@@ -162,8 +162,10 @@ class _SignaturePadState extends State<SignaturePad> {
   Future<Uint8List?> _renderSignatureImage() async {
     try {
       // 创建画布
-      const width = 600.0;
-      const height = 200.0;
+      // 尺寸比例需要匹配PDF签名字段比例（约92:51 ≈ 1.8:1）
+      // 使用较大尺寸保证清晰度
+      const width = 460.0;
+      const height = 255.0;
 
       final recorder = ui.PictureRecorder();
       final canvas = Canvas(recorder, Rect.fromLTWH(0, 0, width, height));