function insert_file($fwqm, $kjsj, $yxts, $jingyan, $version, $xianlu, $kefu, $zhuye)  
    {           
        $this->db->query("SET NAMES utf8"); 
        if($fwqm != null){
            $data = array(
                                    'fwqm' => $this->security->xss_clean($fwqm),
                                    'kjsj' => $this->security->xss_clean($kjsj),
                                    'yxts' => $this->security->xss_clean($yxts),
                                    'version' => $this->security->xss_clean($version),
                                    'jingyan' => $this->security->xss_clean($jingyan),
                                    'xianlu' => $this->security->xss_clean($xianlu),
                                    'kefu' => $this->security->xss_clean($kefu),
                                    'zhuye' => $this->security->xss_clean($zhuye),
                            );

             $this->db->insert('fbz',$data);
        }
    }

直接写中文是可以的，把变量赋值为中文也是可以插入的，通过表单也能插入，但就是这样通过参数传递进来，中文就插入不进mysql,显示空白.

知道了。编码问题
$kjsj = mb_convert_encoding($kjsj,'utf8', 'gbk');