diff --git a/app/static/app.js b/app/static/app.js
index f5dcd99..8d9363b 100644
--- a/app/static/app.js
+++ b/app/static/app.js
@@ -300,7 +300,7 @@
     if (threshold > 0) {
       datasets.push({
         label: "阈值",
-        data: [threshold, threshold],
+        data: hist.map(() => threshold),   // 与 x 轴等长，虚线水平贯穿整图
         borderColor: thColor,
         borderDash: [4, 4],
         pointRadius: 0,