效果图:

 代码:

    <el-form :inline="true" label-width="140px" label-position="right" :model="formInline"
      :class="['form', isEdit ? 'contract-form-noedit' : '']">
      <el-form-item class="form-item-full event">
        <el-button type="primary" @click="btnEdit">编辑</el-button>
      </el-form-item>
      <el-form-item label-width="auto" label="Approved by">
        <el-input v-model="formInline.user" placeholder="Approved by" />
      </el-form-item>
      <el-form-item label="Activity zone">
        <el-select v-model="formInline.region" placeholder="Activity zone">
          <el-option label="Zone one" value="shanghai" />
          <el-option label="Zone two" value="beijing" />
        </el-select>
      </el-form-item>
    </el-form>

因为代码重复所以这些只写了一份

.form {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
}

.el-form--inline .el-form-item {
  flex: 1 0 40%;
  align-items: center;
}

//第一行按钮独占一行
.form-item-full {
  flex: 100% !important;
}

css设置这些就ok了