1、打开 /include/taglib/arclist.lib.php 找到,大概在第338行
else if($orderby == 'rand') $ordersql = " ORDER BY rand()";
在它下面加入一行
else if($orderby == 'idlist') $ordersql = " ORDER BY FIELD(arc.id,$idlist)";
2、dede:arclist idlist='' 标签里加入orderby='idlist'
例如
{dede:arclist idlist='1,2,4,6,10' orderby='idlist'}
<li><a href=http://www.dede58.com/"[field:arcurl/]">[field:id/] - [field:title/]</a></li>
{/dede:arclist}