<a-select
          class="subscribe-select"
          dropdownClassName="drop-down-Style" // 下拉菜单的 className 属性
          :dropdownMatchSelectWidth="false" // 下拉菜单不和选择器同宽
          :value="userId"
          @change="handleUserChange"
          :defaultOpen="true"
        >
          <a-select-option v-for="item in subscribePerson" :value="item.label" :key="item.key">
            {{ item.value }}
          </a-select-option>
        </a-select>

.drop-down-Style {
  width: auto;
}