只要在include\taglib\channel.lib.php    

找到下面黑色代码,加入下面红色代码 description,即可 

位置在78行 

if($type=='top') 
    { 
        $sql = "SELECT id,typename,description,typedir,isdefault,ispart,defaultname,namerule2,moresite,siteurl,sitepath 
          From `dede_arctype` WHERE reid=0 And ishidden<>1 order by sortrank asc limit 0, $line "; 
    } 
    else if($type=='son') 
    { 
        if($typeid==0) return ''; 
        $sql = "SELECT id,typename,description,typedir,isdefault,ispart,defaultname,namerule2,moresite,siteurl,sitepath 
          From `dede_arctype` WHERE reid='$typeid' And ishidden<>1 order by sortrank asc limit 0, $line "; 
    } 
    else if($type=='self') 
    { 
        if($reid==0) return ''; 
        $sql = "SELECT id,typename,description,typedir,isdefault,ispart,defaultname,namerule2,moresite,siteurl,sitepath 
            FROM `dede_arctype` WHERE reid='$reid' And ishidden<>1 order by sortrank asc limit 0, $line "; 
    } 

然后即可调用： 
例如： 
{dede:channel type='son' typeid='21'} 
<p>[field:description/]</p> 
{/dede:channel}