diff --git a/packages/stepper/index.ts b/packages/stepper/index.ts
index 5c96b722..e2f7f0bd 100644
--- a/packages/stepper/index.ts
+++ b/packages/stepper/index.ts
@@ -86,14 +86,14 @@ VantComponent({
       this.triggerInput(value);
     },
 
-    onChange(type) {
+    onChange(type: string) {
       if (this.data[`${type}Disabled`]) {
         this.$emit('overlimit', type);
         return;
       }
 
       const diff = type === 'minus' ? -this.data.step : +this.data.step;
-      const value = Math.round((this.data.value + diff) * 100) / 100;
+      const value = Math.round((+this.data.value + diff) * 100) / 100;
       this.triggerInput(this.range(value));
       this.$emit(type);
     },