方法一、

//和其他一样添加prop属性
<el-form ref="form" :model="form" :rules="rules" label-width="140px">
  <el-form-item label="营业执照上传" prop="imageId">
    <el-upload 
      ref="upload" 
      class="avatar-uploader" 
      :headers="upload.headers" 
      :disabled="upload.isUploading"
      :action="upload.url + '?file=' + upload.updateSupport" 
      :show-file-list="false" 
      :limit="1" 
      accept=".jpg, .jpeg, .png"
      :on-progress="handleFileUploadProgress" 
      :on-success="handleFileSuccess" 
      :on-error="handleFileError"
      :auto-upload="true"
    >
      <img v-if="form.imageId" :src="form.imageUrl" class="avatar" />
      <i v-else class="el-icon-plus avatar-uploader-icon"></i>
    </el-upload>
  </el-form-item>
</el-form>

//data里面添加rules校验规则
rules: {
  imageId: [{ required: true, message: '请上传营业执照', trigger: 'change' }]
},

//在methods里添加图片上传成功的回调方法handleFileSuccess
handleFileSuccess(response, file, fileList) {
  this.form.imageId = response;
  this.form.imageUrl = baseURL + response;
  this.upload.isUploading = false;
  this.$refs.form.clearValidate('imageId') //清除图片校验文字
},

方法二、
此方法是通过一个接口将图片和form表单一次提交到后端，网上大部分都是方法一。

//和其他一样添加prop属性
<el-form ref="form" :model="form" :rules="rules" label-width="140px">
  <el-form-item label="营业执照上传" prop="imageUrl">
    <el-upload 
      ref="upload" 
      class="avatar-uploader" 
      :headers="upload.headers" 
      :disabled="upload.isUploading"
      :action="upload.url + '?file=' + upload.updateSupport" 
      :show-file-list="false" 
      :limit="1" 
      accept=".jpg, .jpeg, .png"
      :on-change="handleFileChange" //添加文件改变时钩子
      :on-progress="handleFileUploadProgress" 
      :on-success="handleFileSuccess" 
      :on-error="handleFileError"
      :auto-upload="false" //改为手动上传
      :data="form" //携带其他参数上传
    >
      <img v-if="form.imageUrl" :src="form.imageUrl" class="avatar" />
      <i v-else class="el-icon-plus avatar-uploader-icon"></i>
    </el-upload>
  </el-form-item>
</el-form>
<div slot="footer" class="dialog-footer">
  <el-button type="primary" @click="submitClick">确 定</el-button>
  <el-button @click="cancelClick">取 消</el-button>
</div>

//data里面添加rules校验规则
rules: {
  imageUrl: [{ required: true, message: '请上传营业执照', trigger: 'change' }]
},
upload: {
  // 是否显示弹出层（用户导入）
  open: false,
  // 弹出层标题（用户导入）
  title: '',
  // 是否禁用上传
  isUploading: false,
  // 是否更新已经存在的用户数据
  updateSupport: 0,
  // 设置上传的请求头部
  headers: { Authorization: getToken() },
  // 上传的地址
  url: baseURL + '/t-mchinfo/add',
  fileList: ''
}

//在methods里添加图片上传成功的回调方法handleFileSuccess
handleFileChange(file, fileList) {
  //判断图片列表长度大于0时，代表已上传本地图片
  if(fileList.length > 0){
    this.form.imageUrl = file.url; //image图片回显
    this.$refs.form.clearValidate('imageUrl') //清除图片文字校验
  }
}
// 对话框点击提交
submitClick() {
  this.$refs['form'].validate(valid => {
    if (valid) {
      this.$refs.upload.submit() //手动提交upload
    }
  });
},