案例 

<template>
  
    <el-form :model="form" ref="form" label-width="70px">
      <el-form-item>
        <el-button icon="el-icon-plus" type="primary" plain @click="add">新增</el-button>
        <el-button @click="resetForm('form')">重置</el-button>
      </el-form-item>
     <el-row :gutter="20" v-for="(user, index) in form.userList">
       <el-col :span="6">
         <el-form-item label="用户"
                       :prop="'userList.' + index + '.userId'"
                       :rules="[
                         {required: true, message: '用户不能为空', trigger: ['blur','change']},
                          { validator: validUser, trigger: ['blur','change'] }
                         ]"
         >
           <el-select 
                      v-model="user.userId"
                      placeholder="请选择用户"
                      
                      >
             <el-option v-for="(item,index) in uList"
                        :label="item.userName" :value="item.userId"  :key="item.userId"></el-option>
           </el-select>
         </el-form-item>
       </el-col>
       <el-col :span="16">
         <el-form-item label="职能"
                       :prop="'userList.' + index + '.roleId'"
                       :rules="{required: true, message: '职能不能为空', trigger: ['blur','change']}"
         >

           <el-select
             v-model="user.roleId"
             multiple
             placeholder="请选择职能"
             
           >
             <el-option
               v-for="dict in dict.type.zhineng_dict"
               :key="dict.value"
               :label="dict.label"
               :value="dict.value"
             ></el-option>
           </el-select>
         </el-form-item>
       </el-col>
       <el-col :span="2" v-if="index !==0">
         <el-button type="danger" icon="el-icon-delete" plain @click.prevent="handleDelete(user)"></el-button>
       </el-col>
     </el-row>

    </el-form>
</template>

<script>


export default {
  name: "",
  dicts: ['zhineng_dict'],
  
  
  data(){
    return {
      // 表单
      form: {
        userList: []
      },
      // 人员列表
      uList: [],
      
    }
  },
  mounted() {
    this.getuList()
    this.setDefault()
  },
  methods: {
    validUser(rule, value, callback){
      let userArr = [];
      this.form.userList.forEach(item => {
        userArr.push(item.userId)
      })

      if (userArr.length !== [...new Set(userArr)].length) {
        callback(new Error('用户不可以重复'));
      }else {
        callback();
      }
    },
    /* 设置默认 */
    setDefault() {
      this.form.userList.push({
        userId: '',
        roleId: [],
        key: Date.now()
      })
    },
    /* 删除 */
    handleDelete(user) {
      var index = this.form.userList.indexOf(user)
      if (index !== -1) {
        this.form.userList.splice(index, 1)
      }
    },
    
    getuList(){
      this.uList= response.data;
    },
    resetForm(formName) {
      this.$refs[formName].resetFields();
    },
    /* 新增 */
    add(){
      this.form.userList.push({
        userId: '',
        roleId: [],
        key: Date.now()
      });
    }
  }
}
</script>

注意

1、select为多选时，默认值需设置为[]，否则未填值前就会报校验错误

2、表单必须为object，不能用[ ]，会报错