你可以试试 .mylast:last-of-type

示例代码：

<style> 
.mylast:last-of-type
{
	background:#ff0000;
}
</style>

<h1>This is a heading</h1>
<div class="mylast">The first paragraph.</div>
<div class="mylast">The second paragraph.</div>
<div class="mylast">The third paragraph.</div>
<div class="mylast">The fourth paragraph.</div>