DEDECMS按照下载次数排序，排序在SQL语句里无非就是order by 下载次数 desc，知道了这个然后我们就看需要改哪里了。 
找到include目录下面的taglib目录里的arclist.lib.PHP文件在376行后加入如下代码 
if($orderby == 'down') 
{ 
$sql = "select SUM(downloads) as down_num,id from dede_downloads group by id ORDER BY down_num DESC LIMIT 0,15"; 
$dsql->Execute('me',$sql); 
while($drow = $dsql->GetArray() ) 
{ 
$arr[] = $drow['id']; 
} 
$dstr = implode(",",$arr); 
if($orwhere!='') 
{ 
$orwhere .= " AND arc.id in($dstr)"; 
}else{ 
$orwhere .= " where arc.id in($dstr)"; 
} 
$ordersql = 'ORDER BY field(arc.id,'.$dstr.')'; 
}