const onImportExcel = (file) => {

    return new Promise(async (resolve, reject) => {

      ...  //要执行的语句

        return reject(false);  //加上这个就会阻止默认上传

    });

  };

    <Upload

          name="file"

          className="avatar-uploader"

          showUploadList={false}

          beforeUpload={onImportExcel}

          accept=".xlsx,.xls,.xlt"

        >

          <Button type="primary" icon={<DownloadOutlined />}>

            导入

          </Button>

        </Upload>