var table=document.getElementsByTagName("table");
var targetVal=table[0].rows[1].cells[1];

One way is to find the cell in the province and then extract the data of the adjacent cells. I use pyquery to parse html. If you have written front-end jquery, you should be familiar with it.

from pyquery import PyQuery as pq
t='''<table width="100%;">
                        <tr>
                <td class="op_trust_tdLeft">执行法院：</td>
                <td class="op_trust_tdRight">福田区人民法院</td>
            </tr>
            <tr>
                <td class="op_trust_tdLeft">省份：</td>
                <td class="op_trust_tdRight">广东</td>
            </tr>
            <tr>
                <td class="op_trust_tdLeft">案号：</td>
                <td class="op_trust_tdRight">(2011)深福法执字第01854号</td>
            </tr>'''
p=pq(t)
print(p.find('.op_trust_tdLeft').filter(lambda i,this: pq(this).text() == '省份：').parent().find('.op_trust_tdRight').text())