OBJECTIVE To investigate the effects of continuous positive airway pressure (CPAP) on patients with severe obstructive sleep apnea hypopnea syndrome (OSAHS) who underwent the revised uvulopalatopharyngoplasty (UPPP). METHODS 18 cases of severe OSAHS patients (therapy group) were selected for CPAP treatment in the 2nd week of postoperation. The average time of CPAP treatment was 34.3 days. The other 20 cases (control group) onlyunderwent operation. All patients were monitored with PSG before operation and in the 6 months postoperatively. RESULTS Compared with the result of pre-operative PSG, apnea hypopnea index (AHI) and Lowest SaO2 (LSaO_2) was improved (P＜0.001) in two groups. Compared with control group, LSaO_2 of the therapy group in the sixth month postoperatively was improved (P＜0.001), but the decreasing of AHI was not significant (P＞0.05). Contrast to the control group, the length of stage 1 and 2 decreased and that of REM increased. (P＜0.05). CONCLUSION For severe OSAHS patients who underwent uvulopalatopharyngo plasty, CPAP treatment for one month postoperatively could improve the hypoxia of patients, and prolong REM stage, shorten the stage 1 and 2 sleep. CPAP treatment in short time would be helpful for the severe OSAHS patients with revised UPPP.