Objective To record the electromyography（EMG） of mandibular prognathism patients before and after orthognathic surgery, analyse the change process of masticatory muscles system after sagittal split ramus osteotomy（ SSRO） and further explore the relationship between the electromyography changes and the adaptive remodeling of masticatory muscles. Methods We selected 18 simply mandibular prognathism patients who will accept SSRO. Recorded the electrophysiological parameters of masticatory muscles before the operation, after 3 months, after 1 year, and then calculated and analysed the parameters. Results The mandibular prognathism patients had lower EMG indexes under normal conditions. 3 months after SSRO, most of EMG indexes came down which were significantly lower than preoperative group. 1 year after SSRO, most of the EMG indexes improved a lot, while some of them were still lower than control group. Conclusion Reconstruction of masticatory muscle system after SSRO is a long-term process. The performance of masticatory muscles was improved by SSRO.
