s='<img src="aaaa/UploadFiles/aaa.jpg"><img src="bbb/UploadFiles/bbb.jpg"><img src="ccc/UploadFiles/ccc.jpg">';
re=/<img src="[^\/]*\/([^"]*)">/gi;
ne='<img src="$1">';
alert(s.replace(re,ne));
才能得到这样的结果
<img src="UploadFiles/aaa.jpg"><img src="UploadFiles/bbb.jpg"><img src="UploadFiles/ccc.jpg">