核心算法：
$('#tableId tr').each(function() {
$(this).find('td:eq(columnIndex)').each(function() {
totalAmount += parseFloat($(this).text());
})
});
完整代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Jquery计算table行合计</title>
<script id="jquery_183" type="text/javascript" class="library" src="http://runjs.cn/js/sandbox/jquery/jquery-1.8.3.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
var totalRow = 0
$('#mytable tr').each(function() {
$(this).find('td:eq(2)').each(function(){
totalRow += parseFloat($(this).text());
});
});
$('#totalRow').append('<td>合计</td><td></td><td>'+totalRow+'</td><td></td>');
});
</script>
</head>
<body style="100%; height:100%;">
<table id="mytable" border="1" width="37%">
<thead>
</thead>
<tr>
<td width="63" >10</td>
<td width="68" >20</td>
<td width="62" >30</td>
<td width="75" >40</td>
</tr>
<tr>
<td width="63" >25</td>
<td width="68" >35</td>
<td width="62" >45</td>
<td width="75" >55</td>
</tr>
<tr id="totalRow"></tr>
</table>
</body>
</html>
效果图：
