想要的效果：

话不多说上代码：

      <!-- table表格 -->
      <el-table :data="tableData" border style="width: 100%" v-loading="loading">
        <el-table-column type="selection" width="55" align="center">
        </el-table-column>
        <el-table-column fixed prop="pumpName" label="泵站名称" width="150" align="center"></el-table-column>
        <el-table-column prop="pointName" label="点位名称"></el-table-column>
        <el-table-column prop="id" label="id"></el-table-column>
        <el-table-column prop="timeHorizon" label="视频时间范围" width="200"></el-table-column>
        <el-table-column prop="createTime" label="下载时间"></el-table-column>
        <el-table-column prop="taskAchievement" label="完成情况">
          <template slot-scope="scope" style="text-align: left">
            <div v-if="scope.row.taskAchievement == '1'">下载中</div>
            <div v-if="scope.row.taskAchievement == '2'">已完成</div>
            <div v-if="scope.row.taskAchievement == '3'">下载失败</div>
          </template>
        </el-table-column>
        <el-table-column prop="path" label="存放路径">
          <el-tage slot-scope="scope" @click="handleCopyLink(scope.row)">
            {{ scope.row.path }}
          </el-tage>
        </el-table-column>
        <el-table-column label="操作" width="200" align="center">
          <template slot-scope="scope">
            <el-button class="table-button" size="small" @click="handleEdit(scope.$index, scope.row)">
              <i class="fa fa-play-circle-o fa-1x" aria-hidden="true"></i>
              <span v-if="scope.row.taskAchievement == '1'">下载中 </span>
              <span v-if="scope.row.taskAchievement == '2'">播放录像</span>
              <span v-if="scope.row.taskAchievement == '3'">重新下载</span>
            </el-button>
            <el-button class="table-button" size="small" @click.native.prevent="deleteRow(scope.$index, scope.row)">
              <i class="fa fa-remove" aria-hidden="true"></i>
              <span>删除</span>
            </el-button>
          </template>
        </el-table-column>
      </el-table>

重点代码：

 总结：通过 v-if指令 决定按钮显示的不同