没想到这个问题到了Discuz! X3了还没解决，不知道官方团队是没注意到这个问题，还是遇到了瓶颈，下面是我搜到的网上的教程，但大部分教程不是隐藏就是需要注册回复，转发到这儿，方便大家直接查阅。

修改文件：source/include/spacecp/spacecp_usergroup.php

找到代码：

$groupexpirynew = $groupterms['ext'][$groupid];

替换为：

$groupexpirynew = $groupterms['ext'][$extgroupidsnew];

找到代码：

$expirylist[$group['groupid']]['grouptitle'] = in_array($group['groupid'], $expgrouparray) ? '' : $group['grouptitle'];

}

}

因为不同版本代码有变，所以如果搜不到全部，就只搜一下：

$expirylist[$group['groupid']]['grouptitle']

在这段代码下面（注意：一定是在两个大括号之后）添加：

if($expgrouparray) {

$extgroupidarray = array();

foreach(explode("t", $_G['forum_extgroupids']) as $extgroupid) {

if(($extgroupid = intval($extgroupid)) && !in_array($extgroupid, $expgrouparray)) {

$extgroupidarray[] = $extgroupid;

}

}

$groupidnew = $_G['groupid'];

$adminidnew = $_G['adminid'];

foreach($expgrouparray as $expgroupid) {

if($expgroupid == $_G['groupid']) {

if(!empty($groupterms['main']['groupid'])) {

$groupidnew = $groupterms['main']['groupid'];

$adminidnew = $groupterms['main']['adminid'];

} else {

$groupidnew = DB::result_first("SELECT groupid FROM ".DB::table('common_usergroup')." WHERE type='member' AND '".$_G['member']['credits']."'>=creditshigher AND '$credits'<creditslower LIMIT 1");

if(in_array($_G['adminid'], array(1, 2, 3))) {

$query = DB::query("SELECT groupid FROM ".DB::table('common_usergroup')." WHERE groupid IN (".dimplode($extgroupidarray).") AND radminid='$_G[adminid]' LIMIT 1");

$adminidnew = (DB::num_rows($query)) ? $_G['adminid'] : 0;

} else {

$adminidnew = 0;

}

}

unset($groupterms['main']);

}

unset($groupterms['ext'][$expgroupid]);

}

require_once libfile('function/forum');

$groupexpirynew = groupexpiry($groupterms);

$extgroupidsnew = implode("t", $extgroupidarray);

$grouptermsnew = addslashes(serialize($groupterms));

DB::query("UPDATE ".DB::table('common_member')." SET adminid='$adminidnew', groupid='$groupidnew', extgroupids='$extgroupidsnew', groupexpiry='$groupexpirynew' WHERE uid='$_G[uid]'");

DB::query("UPDATE ".DB::table('common_member_field_forum')." SET groupterms='$grouptermsnew' WHERE uid='$_G[uid]'");

}

正常情况下，直接生效，但如果看不出来变化，就后台更新一下缓存，就OK了。