//給table,td定最小寬度
table.sheetbody{table-layout: fixed;min-width: 100%;}
td,th{
min-width: 100px;
}
<table border="1" cellspacing="0" cellpadding="0" class="sheetbody">
<colgroup>
<col width="200" span="2" style="background:#3769c3;">
<col width="200" style="background:#628ad2;">
<col width="100" span="5">
</colgroup>
<tr>
<th colspan="2" rowspan="2" scope="col" class="date">Date ending on</th>
<th colspan="2" scope="col">PRC</th>
<th rowspan="2" scope="col"> </th>
<th colspan="2" scope="col">OVERSEAS</th>
</tr>
<tr>
<!--prc-->
<th scope="col"><div class="elli">wk end<span>6/7/2019</span></div></th>
<th scope="col"><div class="elli">wk end<span>6/7/2019</span></div></th>
<!--overseas-->
<th scope="col"><div class="elli">wk end<span>6/7/2019</span></div></th>
<th scope="col"><div class="elli">wk end<span>6/7/2019</span></div></th>
</tr>
<tr>
<td><p>Committed - Outflow</p></td>
<td>22</td>
<td>11</td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>
</table>