效果图：

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui@2.15.6/lib/index.js"></script>
<div id="app">
<template>
  <el-select v-model="value" placeholder="请选择">
    <el-option
      v-for="item in cities"
      :key="item.value"
      :label="item.label"
      :value="item.value">
        //内容两行显示
      <span style="float: left; font-size: 10px;margin-top:-6px;">{{ item.label }}</span>
      <span style="float: left;display:block;position:absolute;margin-top:5px; color: green; font-size: 10px">{{ item.value }}</span>
      
    </el-option>
  </el-select>
</template>
</div>




var Main = {
    data() {
      return {
        cities: [{
          value: 'Beijing',
          label: '北京'
        }, {
          value: 'Shanghai',
          label: '上海'
        }, {
          value: 'Nanjing',
          label: '南京'
        }, {
          value: 'Chengdu',
          label: '成都'
        }, {
          value: 'Shenzhen',
          label: '深圳'
        }, {
          value: 'Guangzhou',
          label: '广州'
        }],
        value: ''
      }
    }
  }
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')