Objective In order to reduce the effect of muscle relaxant on the sensitivity of facial motor evoked potential （FNMEP） during operation of acoustic schwannoma， train of four stimulation （train of four stimulation， TOF） monitoring were used to judge the metabolism of muscle relaxant drugs in real time. Methods Using Cadwell 16 channel intraoperative neuroelectrophysiological monitor， the TOF combined with routine intraoperative neuroelectrophysiological monitoring was used in our hospital from May 2020 to November 2020 to monitor the real-time FNMEP of 12 patients with acoustic neurilemmoma treated by microsurgery. Results All 12 patients were followed up after operation， routine intraoperative neuroelectrophysiological monitoring and FNMEP monitoring were performed when TOF （T4/T1） were greater than or equal to 50%. Follow-up period was 5 to 6 months. Most of the patients recovered their facial nerve function from 2 weeks after surgery， among them there were 3 cases of grade Ⅰ （25%）， 6 cases of grade Ⅱ （50%）， 2 cases of grade Ⅲ （17%）， 1 case of grade Ⅳ （8%）， none cases of Ⅴ， Ⅵ， and deaths. Conclusions The implementation of FNMEP monitoring at a TOF value of more than or equal to 50% may help to improve the sensitivity of intraoperative FNMEP and improve the facial nerve retention rate.