Objective  To study the clinical features of acute respiratory failure induced by obesity hypoventilation syn~drome(OHS).Method  Clinical and laboratory features of 8 patients were reviewed.Results  8 patients(7 male,1 female)with obesity presented a BMI of 38.79 kg·m    -2   in female and 42.68?kg·m    -2   in male.The mean age of the patients was 62 years old.They all had respiratory acidosis(mean pH?7.19),hypercapnia(mean PaCO  2?12.35?kPa),and hypoxemia(mean PaO  2?5.40?kPa).Pulmonary function test showed that the forced expiratory volume in one second to forced vital capacity ratio(FEV  1%) was   78.75  % and the vital capacity ratio(VC%) was 78.80%.During period of clinical stability all had awake hypercapnia (mean PaCO  2?6.49?kPa),and hypoxemia(mean PaO  2?11.42?kPa).Conclusion  Acute respiratory failure induced by OHS has a sudden onset,various presentation and a little lesion to pulmonary function so it can be reversed with early and proper treatment.