diff --git a/src/index.js b/src/index.js
index 03908c0..a4c4123 100644
--- a/src/index.js
+++ b/src/index.js
@@ -63,7 +63,7 @@ export class Component extends HTMLElement {
       },
       enumerable: false
     }
-
+    this.prototype[key] = options.default
     this[__props__].set(name, options)
     Object.defineProperty(this.prototype, name, descriptor)
   }
@@ -102,11 +102,7 @@ export class Component extends HTMLElement {
     this.root = this.shadowRoot || this.attachShadow({ mode: 'open' })
 
     this[__changed_props__] = new Map() // 记录本次变化的属性
-    // 初始化 props
-    this.constructor[__props__].forEach((options, prop) => {
-      this[prop] = options.default
-    })
-    // 若无定义props时, 手动执行一次渲染
+    // 手动执行一次渲染
     if (this[__pending__] === false) {
       this[__pending__] = true
       nextTick(_ => this[__updated__]())
@@ -132,7 +128,7 @@ export class Component extends HTMLElement {
     if (old === val) {
       return
     }
-    this[__attr2prop__](name, val)
+    this[__attr2prop__](name, val, old)
   }
 
   /**
@@ -173,9 +169,8 @@ export class Component extends HTMLElement {
    * @param name<String>
    * @param value<String|Boolean|Number>
    */
-  [__attr2prop__](name, value) {
+  [__attr2prop__](name, value, old) {
     let options = this.#getPropOptions(name)
-
     this[name] = fixedValue(value, options)
   }