Objective This study aims to investigate the efficacy of mandibular advancement oral appliance（OA）for COMISA. Methods 14 patients with COMISA were selected as a comorbid group and 17 with primary snoring as a control group. All the patients were treated in the People′s Hospital of Guangxi Zhang Autonomous Region from April 2013 to August 2019. The polysomnography（PSG）parameters in the comorbid group before OA treatment and one month after treatment and those in the control group to treatment were compared. Results After OA treatment，sleep latency（SL），arousal index（ArI），apnea index（AI），apnea hypopnea index（AHI）decreased （P < 0.05），while total sleep time（TST），sleep efficiency（SE），N3 phase and lowest oxygen saturation（LSpO2） increased in the comorbid group（P < 0.05）. As compared with the control group，the percentage of SL，ArI，N1， TST，SE and N2 was larger in the comorbid group before treatment，but the percentage of TST，SE and N2 was smaller. After treatment，REM sleep latency and ArI were larger，and TST and SE were smaller in the comorbid group（P < 0.05）. Conclusions Oral appliance is a better therapy for COMISA.