diff --git a/index.html b/index.html
index 4314a88..c012a27 100644
--- a/index.html
+++ b/index.html
@@ -278,6 +278,7 @@ <h1>mobile-select demo</h1>
           { data: numArr },
           { data: numArr },
           { data: numArr },
+          { data: numArr },
           { data: numArr }
         ],
         position: [0, 1, 0, 1, 0],
diff --git a/src/ms-core.ts b/src/ms-core.ts
index 6d74da1..0426ed7 100644
--- a/src/ms-core.ts
+++ b/src/ms-core.ts
@@ -4,7 +4,7 @@ import {
   CascadeData,
   OptionData
 } from "./types";
-import { checkIsPC } from "./utils/tools";
+import { checkIsPC, getFloorFloatStr } from "./utils/tools";
 import "./style/mobile-select.less";
 
 export default class MobileSelect {
@@ -614,7 +614,8 @@ export default class MobileSelect {
   }
 
   fixRowStyle(): void {
-    // 自定义列宽度比例 用width不用flex的原因是可以做transition过渡
+    // 自定义列宽度比例
+    // 用width而不用flex的原因: flex虽然可以从num1到num2做transition宽度过渡, 但新增一列时，存量列的宽度无过渡效果
     if (
       this.initColWidth.length &&
       this.initColWidth.length === this.wheelList.length
@@ -622,13 +623,13 @@ export default class MobileSelect {
       const widthSum = this.initColWidth.reduce((cur, pre) => cur + pre, 0);
       this.initColWidth.forEach((item, index) => {
         this.wheelList[index].style.width =
-          ((item / widthSum) * 100).toFixed(2) + "%";
+          getFloorFloatStr(item / widthSum) + "%";
       });
       return;
     }
-    const width = (100 / this.wheelList.length).toFixed(2);
+    const itemWidthStyle = getFloorFloatStr(100 / this.wheelList.length) + "%";
     for (let i = 0; i < this.wheelList.length; i++) {
-      this.wheelList[i].style.width = width + "%";
+      this.wheelList[i].style.width = itemWidthStyle;
     }
   }
 
diff --git a/src/utils/tools.ts b/src/utils/tools.ts
index 8b351c8..afd9051 100644
--- a/src/utils/tools.ts
+++ b/src/utils/tools.ts
@@ -1,7 +1,17 @@
-export function checkIsPC() {
+export function checkIsPC(): boolean {
   return !navigator.userAgent
     .toLowerCase()
     .match(
       /ipad|iphone os|midp|rv:1.2.3.4|ucweb|android|windows ce|windows mobile/
     );
 }
+
+/**
+ * 获取向下取整的小数
+ * @param num 待处理的数 e.g. 16.999
+ * @param digits 保留位数 2
+ * @returns '16.99'
+ */
+export function getFloorFloatStr(num: number, digits = 2): string {
+  return (Math.floor(num * 100) / 100).toFixed(digits);
+}