<table class="table table-bordered">
   <thead>
     <tr>
       <th class="center" style='width:38%;'>商品名称</th>
       <th class="center" style='width:36%;'>详细介绍</th>
       <th class="center" style='width:22%;'>购买数量</th>
     </tr>
   </thead>
   <tbody id="tbody">
     <tr>
      <td>自由行机票享超值优惠</td>
      <td>随心所欲安排行程</td>
      <td>70</td>
    </tr>
    <tr>
      <td>自由行机票享超值优惠</td>
      <td>随心所欲安排行程</td>
      <td>70</td>
    </tr>   
    <tr>
      <td>自由行机票享超值优惠</td>
      <td>随心所欲安排行程</td>
      <td>70</td>
    </tr>            
   </tbody>               
 </table>
.table tbody tr td{
   overflow: hidden; 
   text-overflow:ellipsis; 
   white-space: nowrap; 
 }

<table class="table table-bordered" style='table-layout:fixed;'>

table{
 table-layout:fixed;
}