<el-upload
              class="upload-demo"
              ref="upload"
              action="/datastatistics/file/upload"
              :on-remove="handleRemove"
              :on-success="uploadSuccess"
              :on-error="uploadFaild"
              :before-remove="beforeRemove"
              multiple
              :limit="1"
              :on-exceed="handleExceed"
              :before-upload="beforeUpload"
              :headers="headers"
              :file-list="fileList">
              <el-button slot="trigger" size="small" type="primary" icon="el-icon-upload">点击上传</el-button>
              <el-button type="success" @click="submit" icon="el-icon-document" style="margin-left: 100px">导入
              </el-button>
            </el-upload>

当上传的时候判断上传文件的类型不通过的时候，会触发before-remove，接着触发on-remove方法，解决办法就是，在删除的时候判断下，该文件是不是已经成功上传，如果是的话才可以删除：

    beforeUpload(file) {
        let extension = file.name.substring(file.name.lastIndexOf('.') + 1);
        const acceptFiles = ["xls", "xlsx"];
        if (acceptFiles.indexOf(extension) == -1) {
             this.$message.warning('只能上传EXCEL格式的文件');
              return false;
        }
    },
    //删除文件之前
    beforeRemove(file, fileList) {
      if (file && file.status==="success") {
         ......
      }
    },
    //删除文件
    handleRemove(file, fileList) {
      if (file && file.status==="success") {
        ......
      }
    },

转载：https://blog.csdn.net/xiaoxiangzi520?type=blog