npm install vue-print-nb --save

import Print from 'vue-print-nb'

Vue.use(Print);

<el-dialog title="打印页面" :visible.sync="dialogVisible" width="40%" :loading="loading" size='small' @open="dialogOpen">

     <div style="width:500px">

       <img  id="printTest" :src="printImg" style="width:100%;  height:auto;" >

     </div>

    <span slot="footer" class="dialog-footer">

      <el-button @click="dialogVisible = false">取 消</el-button>

      <el-button type="primary" @click="print" v-print="'#printTest'">去打印</el-button>

    </span>

  </el-dialog>