打开/include/taglib/arclist.lib.php文件
找到376行后加入下面代码 
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.')'; 
}