try  .native.treat  
 Why don't you handle it in onchange 
 
The 
 .update modifier does not delay the completion of the data update. In fact, the data bound by your v-model is still updated, but it is not displayed in data, but watch can still listen, so it will still trigger watch, even if you use the .notify modifier 
 to achieve the function you want, you can define an intermediate amount overload and then handle it in the v-on:change event. Look at the code 
<el-input 
    v-on:change="changeGrabAmount"
    v-model="tmp" 
    :disabled="disableBtnGrabmount"
    >
</el-input>
data() {
    return {
        tmp: "",
        dialogParam: {
          grabAmount: ""
        }
    };
},
methods: {
    changeGrabAmount(val){
        this.dialogParam.grabAmount = val
    }
},
watch:{
    "dialogParam.grabAmount": function(val) {
        //...
     }
}
  the first line of the Element component is explained in the first line of the input input box component on the Chinese official website. The  v-model  modifier is not supported.  
 ex: 
 Input is a controlled component, and it  always displays the Vue binding value . 
 in general, you should handle the  input  event and update the binding value of the component (or use  v-model ). Otherwise, the value displayed in the input box will not change. 
The 
 v-model  modifier is not supported for 
.