<el-table
      ref="multipleTable"
      row-key="id"
      :data="tableData"
      tooltip-effect="dark"
      style="width: 100%"
      @selection-change="handleSelectionChange">
      <el-table-column
      reserve-selection
      type="selection"
      width="55">
      </el-table-column>
      <el-table-column
      label="日期"
      width="120">
      <template slot-scope="scope">{{ scope.row.date }}</template>
      </el-table-column>
      <el-table-column
      prop="name"
      label="姓名"
      width="120">
      </el-table-column>
      <el-table-column
      prop="address"
      label="地址"
      show-overflow-tooltip>
      </el-table-column>
  </el-table>
  <div style="margin-top: 20px">
      <el-button @click="toggleSelection([tableData[1], tableData[2]])">切換第二、第三行的選中狀態</el-button>
      <el-button @click="toggleSelection()">取消選擇</el-button>
  </div>

主要是添加 row-key="id"和 reserve-selection ：僅對 type=selection 的列有效，類型為 Boolean，為 true 則會在數據更新之后保留之前選中的數據（需指定 row-key的值唯一）

      toggleSelection(rows) {
        if (rows) {
          rows.forEach(row => {
            this.$refs.multipleTable.toggleRowSelection(row);
          });
        } else {
          this.$refs.multipleTable.clearSelection();
        }
      },
      handleSelectionChange(val) {
        this.multipleSelection = val;
      },