修改includes/lib_goods.php，改写下两个函数。

/**
* 获得指定分类同级的所有分类以及该分类下的子分类
*
* @access public
* @param   integer     $cat_id     分类编号
* @return array
*/
function get_categories_tree($cat_id = 0)
{
    if ($cat_id > 0)
    {
        $sql = 'SELECT parent_id FROM ' . $GLOBALS['ecs']->table('category') . " WHERE cat_id = '$cat_id'";
        $parent_id = $GLOBALS['db']->getOne($sql);
    }
    else
    {
        $parent_id = 0;
    }
    /*
     判断当前分类中全是是否是底级分类，
     如果是取出底级分类上级分类，
     如果不是取当前分类及其下的子分类
    */
    $sql = 'SELECT count(*) FROM ' . $GLOBALS['ecs']->table('category') . " WHERE parent_id = '$parent_id' AND is_show = 1 ";
    if ($GLOBALS['db']->getOne($sql) || $parent_id == 0)
    {
        /* 获取当前分类及其子分类 */
        $sql = 'SELECT cat_id,cat_name ,parent_id,is_show ' .
                'FROM ' . $GLOBALS['ecs']->table('category') .
                "WHERE parent_id = '$parent_id' AND is_show = 1 ORDER BY sort_order ASC, cat_id ASC";
        $res = $GLOBALS['db']->getAll($sql);

   $sql = "SELECT cat_id, COUNT(*) AS goods_num " .
   " FROM " . $GLOBALS['ecs']->table('goods') . " AS g " .
   " GROUP BY cat_id";

    $res2 = $GLOBALS['db']->getAll($sql);
    $newres = array();
    foreach($res2 AS $row)
    {
     $newres[$row['cat_id']] = $row['goods_num'];
    }

        foreach ($res AS $row)
        {
            if ($row['is_show'])
            {
                $cat_arr[$row['cat_id']]['id']   = $row['cat_id'];
        $cat_arr[$row['cat_id']]['num'] = !empty($newres[$row['cat_id']]) ? $newres[$row['cat_id']] : 0;
                $cat_arr[$row['cat_id']]['name'] = $row['cat_name'];
                $cat_arr[$row['cat_id']]['url'] = build_uri('category', array('cid' => $row['cat_id']), $row['cat_name']);
                if (isset($row['cat_id']) != NULL)
                {
                    $cat_arr[$row['cat_id']]['cat_id'] = get_child_tree($row['cat_id']);
                }
            }
        }
    }
    if(isset($cat_arr))
    {
        return $cat_arr;
    }
}
function get_child_tree($tree_id = 0)
{
    $three_arr = array();
    $sql = 'SELECT count(*) FROM ' . $GLOBALS['ecs']->table('category') . " WHERE parent_id = '$tree_id' AND is_show = 1 ";
    if ($GLOBALS['db']->getOne($sql) || $tree_id == 0)
    {
        $child_sql = 'SELECT cat_id, cat_name, parent_id, is_show ' .
                'FROM ' . $GLOBALS['ecs']->table('category') .
                "WHERE parent_id = '$tree_id' AND is_show = 1 ORDER BY sort_order ASC, cat_id ASC";
        $res = $GLOBALS['db']->getAll($child_sql);

   $sql = "SELECT cat_id, COUNT(*) AS goods_num " .
   " FROM " . $GLOBALS['ecs']->table('goods') . " AS g " .
   " GROUP BY cat_id";
    $res2 = $GLOBALS['db']->getAll($sql);
    $newres = array();
    foreach($res2 AS $row)
    {
     $newres[$row['cat_id']] = $row['goods_num'];
    }

        foreach ($res AS $row)
        {
            if ($row['is_show'])
       $three_arr[$row['cat_id']]['num'] = !empty($newres[$row['cat_id']]) ? $newres[$row['cat_id']] : 0;
               $three_arr[$row['cat_id']]['id']   = $row['cat_id'];
               $three_arr[$row['cat_id']]['name'] = $row['cat_name'];
               $three_arr[$row['cat_id']]['url'] = build_uri('category', array('cid' => $row['cat_id']), $row['cat_name']);
               if (isset($row['cat_id']) != NULL)
                   {
                       $three_arr[$row['cat_id']]['cat_id'] = get_child_tree($row['cat_id']);
            }
        }
    }
    return $three_arr;
}

2.修改category_tree.lib库，写入num变量。

<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<div class="box">
<div class="box_1">
<div id="category_tree">
<!--{foreach from=$categories item=cat}-->
<dl>
<dt><a href="{$cat.url}">{$cat.name|escape:html}</a>({$cat.num})</dt>
<!--{foreach from=$cat.cat_id item=child}-->
<dd><a href="{$child.url}">{$child.name|escape:html}</a>({$child.num})</dd>
<!--{foreach from=$child.cat_id item=childer}-->
<dd> <a href="{$childer.url}">{$childer.name|escape:html}</a>({$childer.num})</dd>
<!--{/foreach}-->
<!--{/foreach}-->

</dl>
<!--{/foreach}-->
</div>
</div>