效果图

解决
:append-to-body="false"添加这个属性就可以了

<el-popover
                v-model="item.contextmenuVisible"
                placement="bottom-end"
                :append-to-body="false"
                trigger="click"
                :visible-arrow="false"
                @hide="item.contextBtnVisible = false"
              >
                <ul
                  @mouseover="item.contextBtnVisible = true"
                  @mouseleave="!item.contextmenuVisible?item.contextBtnVisible = false:null"
                >
                  <li v-show="pageType === 'drafts'||pageType === 'error'||pageType === 'remove'" @click="handleTips(item,0)">删除</li>
                  <li v-show="pageType === 'loading'" @click="handleTips(item,1)">取消发布</li>
                  <li v-show="pageType === 'drafts'" @click="handleCopy(item,index)">复制</li>
                  <li v-show="pageType === 'remove'" @click="handleTips(item,2)">上架</li>
                  <li v-show="pageType === 'release'" @click="handleTips(item,3)">下架</li>
                </ul>
                <span slot="reference" @click.stop="clickContextmenu(index)">
                  <img alt="拓展" src="@/assets/images/icon-gengduocopy@2x.png" class="context-btn">
                </span>
              </el-popover>