1.首先给el-form添加一个class

<el-form ref="form" :model="form" label-width="80px" class="frame">
  <el-form-item label="活动名称">
    <el-input v-model="form.name"></el-input>
  </el-form-item>
  <el-form-item label="活动区域">
    <el-select v-model="form.region" placeholder="请选择活动区域">
      <el-option label="区域一" value="shanghai"></el-option>
      <el-option label="区域二" value="beijing"></el-option>
    </el-select>
  </el-form-item>
</el-form>

 2.直接在style中写

.frame{
    .el-form-item {
      .el-input {
        width: 70px;
      }
      .el-select{
        width: 70px;
      }
    }
  }