diff --git a/backend/services/planting-service/src/infrastructure/pdf/pdf-generator.service.ts b/backend/services/planting-service/src/infrastructure/pdf/pdf-generator.service.ts
index 40ec832a..e1b7f952 100644
--- a/backend/services/planting-service/src/infrastructure/pdf/pdf-generator.service.ts
+++ b/backend/services/planting-service/src/infrastructure/pdf/pdf-generator.service.ts
@@ -389,64 +389,59 @@ export class PdfGeneratorService {
       this.logger.log('Using form fields mode');
       await this.fillFormFields(pdfDoc, data, customFont);
 
-      // 5. 如果有签名，嵌入签名图片到 signature 按钮字段
+      // 5. 如果有签名，嵌入签名图片
+      // 直接使用坐标方式在页面上绘制签名，不受表单字段尺寸限制
       if (signature) {
         const signatureImage = await pdfDoc.embedPng(signature.signatureImagePng);
 
+        // 获取签名字段位置作为参考
+        let signatureX = 380; // 默认 x 坐标
+        let signatureY = 100; // 默认 y 坐标
+
         try {
           const form = pdfDoc.getForm();
           const signatureButton = form.getButton(FORM_FIELDS.SIGNATURE);
-
-          // 获取按钮的 widget 和尺寸
           const widgets = signatureButton.acroField.getWidgets();
           if (widgets.length > 0) {
-            const widget = widgets[0];
-            const rect = widget.getRectangle();
-            const { width: fieldWidth, height: fieldHeight } = rect;
-
-            // 计算图片缩放尺寸（保持宽高比，适应字段大小）
-            const imgDims = signatureImage.scale(1);
-            const scale = Math.min(fieldWidth / imgDims.width, fieldHeight / imgDims.height);
-            const scaledWidth = imgDims.width * scale;
-            const scaledHeight = imgDims.height * scale;
-
-            // 计算居中位置
-            const x = (fieldWidth - scaledWidth) / 2;
-            const y = (fieldHeight - scaledHeight) / 2;
-
-            // 创建外观流内容
-            const appearanceStream = `q ${scaledWidth} 0 0 ${scaledHeight} ${x} ${y} cm /Img Do Q`;
-
-            // 创建 XObject Form 作为外观
-            const context = pdfDoc.context;
-            const imageXObjectName = 'Img';
-
-            const Resources = context.obj({
-              XObject: { [imageXObjectName]: signatureImage.ref },
-            });
-
-            const appearanceStreamRef = context.register(
-              context.stream(appearanceStream, {
-                Type: 'XObject',
-                Subtype: 'Form',
-                FormType: 1,
-                BBox: [0, 0, fieldWidth, fieldHeight],
-                Resources,
-              }),
-            );
-
-            // 设置外观到 widget
-            widget.setNormalAppearance(appearanceStreamRef);
-
-            this.logger.log(`Signature embedded using custom appearance stream, field size: ${fieldWidth}x${fieldHeight}`);
-          } else {
-            throw new Error('No widgets found for signature button');
+            const rect = widgets[0].getRectangle();
+            // 使用字段左下角作为签名位置参考
+            signatureX = rect.x;
+            signatureY = rect.y;
+            this.logger.log(`Signature field position: x=${rect.x}, y=${rect.y}, field size: ${rect.width}x${rect.height}`);
           }
-        } catch (error) {
-          // 如果没有签名按钮字段，回退到坐标方式
-          this.logger.log(`Signature button field error: ${error.message}, using coordinates`);
-          this.embedSignatureByCoordinates(pdfDoc, signatureImage);
+        } catch {
+          this.logger.log('No signature button field found, using default coordinates');
         }
+
+        // 直接在页面上绘制签名图片
+        const pages = pdfDoc.getPages();
+        const lastPage = pages[pages.length - 1];
+
+        // 计算签名图片的尺寸（保持宽高比，目标尺寸更大）
+        const maxWidth = 150;
+        const maxHeight = 80;
+        const { width, height } = signatureImage.scale(1);
+        let scaledWidth = width;
+        let scaledHeight = height;
+
+        if (width > maxWidth) {
+          scaledWidth = maxWidth;
+          scaledHeight = (height * maxWidth) / width;
+        }
+        if (scaledHeight > maxHeight) {
+          scaledHeight = maxHeight;
+          scaledWidth = (width * maxHeight) / height;
+        }
+
+        // 在签名位置绘制图片
+        lastPage.drawImage(signatureImage, {
+          x: signatureX,
+          y: signatureY,
+          width: scaledWidth,
+          height: scaledHeight,
+        });
+
+        this.logger.log(`Signature drawn at (${signatureX}, ${signatureY}), size: ${scaledWidth}x${scaledHeight}`);
       }
 
       // 6. 最后统一扁平化所有表单字段