diff --git a/tauri-app/src/pages/VideoCreation/SubtitleBurning.tsx b/tauri-app/src/pages/VideoCreation/SubtitleBurning.tsx
index 45a63e7..9268b97 100644
--- a/tauri-app/src/pages/VideoCreation/SubtitleBurning.tsx
+++ b/tauri-app/src/pages/VideoCreation/SubtitleBurning.tsx
@@ -188,47 +188,56 @@ export default function SubtitleBurning() {
   // 构建 ASS Style 参数
   const videoDurationMs = (alignment?.duration || 0) * 1000;
 
-  const buildSubtitleStyle = (preset: TitlePreset, scale: number = 1): Partial<AssStyle> => ({
-    fontSize: Math.round(64 * scale),
-    primaryColor: htmlColorToAss(preset.primaryColor),
-    outlineColor: htmlColorToAss(preset.outlineColor),
-    backColor: htmlColorToAss(preset.backColor),
-    borderStyle: preset.borderStyle,
-    outline: Math.round(preset.outline * scale),
-    shadow: 0,
-    alignment: 2,
-    marginV: Math.round(480 * scale),
-    marginL: Math.round(160 * scale),
-    marginR: Math.round(160 * scale),
-  });
+  const buildSubtitleStyle = (preset: TitlePreset, scale: number = 1): Partial<AssStyle> => {
+    const is720 = scale <= 0.7;
+    return {
+      fontSize: is720 ? 40 : 64,
+      primaryColor: htmlColorToAss(preset.primaryColor),
+      outlineColor: htmlColorToAss(preset.outlineColor),
+      backColor: htmlColorToAss(preset.backColor),
+      borderStyle: preset.borderStyle,
+      outline: Math.round(preset.outline * scale),
+      shadow: 0,
+      alignment: 2,
+      marginV: Math.round(480 * scale),
+      marginL: Math.round(160 * scale),
+      marginR: Math.round(160 * scale),
+    };
+  };
 
-  const buildMainTitleStyle = (preset: TitlePreset, scale: number = 1): Partial<AssStyle> => ({
-    fontSize: Math.round(96 * scale),
-    primaryColor: htmlColorToAss(preset.primaryColor),
-    outlineColor: htmlColorToAss(preset.outlineColor),
-    backColor: htmlColorToAss(preset.backColor),
-    borderStyle: preset.borderStyle,
-    outline: Math.round(preset.outline * scale),
-    shadow: 0,
-    alignment: 8,
-    marginV: Math.round(320 * scale),
-    marginL: Math.round(160 * scale),
-    marginR: Math.round(160 * scale),
-  });
+  const buildMainTitleStyle = (preset: TitlePreset, scale: number = 1): Partial<AssStyle> => {
+    const is720 = scale <= 0.7;
+    return {
+      fontSize: is720 ? 64 : 90,
+      primaryColor: htmlColorToAss(preset.primaryColor),
+      outlineColor: htmlColorToAss(preset.outlineColor),
+      backColor: htmlColorToAss(preset.backColor),
+      borderStyle: preset.borderStyle,
+      outline: Math.round(preset.outline * scale),
+      shadow: 0,
+      alignment: 8,
+      marginV: Math.round(320 * scale),
+      marginL: Math.round(160 * scale),
+      marginR: Math.round(160 * scale),
+    };
+  };
 
-  const buildSubTitleStyle = (preset: TitlePreset, scale: number = 1): Partial<AssStyle> => ({
-    fontSize: Math.round(80 * scale),
-    primaryColor: htmlColorToAss(preset.primaryColor),
-    outlineColor: htmlColorToAss(preset.outlineColor),
-    backColor: htmlColorToAss(preset.backColor),
-    borderStyle: preset.borderStyle,
-    outline: Math.round(preset.outline * scale),
-    shadow: 0,
-    alignment: 8,
-    marginV: Math.round(440 * scale),
-    marginL: Math.round(160 * scale),
-    marginR: Math.round(160 * scale),
-  });
+  const buildSubTitleStyle = (preset: TitlePreset, scale: number = 1): Partial<AssStyle> => {
+    const is720 = scale <= 0.7;
+    return {
+      fontSize: is720 ? 50 : 72,
+      primaryColor: htmlColorToAss(preset.primaryColor),
+      outlineColor: htmlColorToAss(preset.outlineColor),
+      backColor: htmlColorToAss(preset.backColor),
+      borderStyle: preset.borderStyle,
+      outline: Math.round(preset.outline * scale),
+      shadow: 0,
+      alignment: 8,
+      marginV: Math.round(440 * scale),
+      marginL: Math.round(160 * scale),
+      marginR: Math.round(160 * scale),
+    };
+  };
 
   // 用 text-shadow 模拟 ASS 外描边（比 WebkitTextStroke 的居中描边更准确）
   const getOutlineShadow = (color: string, outlineWidth: number): string => {
@@ -391,10 +400,12 @@ export default function SubtitleBurning() {
 
       if ((mainTitle && mtStyle) || (subTitle && stStyle)) {
         const { generateTitlePngDataUrl } = await import('../../utils/titlePngGenerator');
+        // 标题 PNG 使用独立的字体大小（与 ASS 不同）
+        const titlePngMainStyle = mtStyle ? { ...mtStyle, fontSize: targetWidth === 720 ? 64 : 104 } : undefined;
         const pngDataUrl = await generateTitlePngDataUrl(
           mainTitle || undefined,
           subTitle || undefined,
-          mtStyle,
+          titlePngMainStyle,
           stStyle,
           targetWidth,
           targetHeight,