Aim To investigate the correlation between severity of coronary artery lesions and middle-term prognosis with obstructive sleep apnea-hypopnea syndrome(OSAHS) in patients with acute coronary syndrome(ACS). Methods The patients with ACS were classified into four groups according to results of coronary angiography and polysomnography: ACS group(group Ⅰ),ACS complicated with mild OSAHS(group Ⅱ),ACS complicated with moderate OSAHS(group Ⅲ),ACS complicated with severe OSAHS(group Ⅳ).Coronary artery lesions' severity was compared by Gensini score.The relationship between Gensini score and apnea hypopnea index(AHI) and nocturunal lowest blood oxygen saturation(LSaO2) were analyzed.The patients were followed up for six months,and the amounts of cardiovascular composite endpoint in four groups were compared. Results Compared with group Ⅰ,AHI of group Ⅱ,Ⅲ and Ⅳ were much higher(P<0.01),LSaO2 of group Ⅱ,Ⅲ and Ⅳ were much lower(P<0.01).Compared with group Ⅱ,AHI of group Ⅲ and Ⅳ were much higher(P<0.01),LSaO2 of group Ⅲ and Ⅳ were much lower(P<0.01).Compared with group Ⅱ and Ⅰ,Gensini scores of group Ⅲ and Ⅳ were much higher(P<0.01).Gensini score of group Ⅳ was higher than group Ⅲ(P<0.05).Gensini score was positively correlated with AHI and negatively with LSaO2.Incidence of cardiovascular composite endpoint events during six months in four groups were 19.35%,22.58%,32.26%,43.33% respectively.The group Ⅳ's cardiovascular composite endpoint events was higher than group Ⅰ(P<0.05).Total cholesterol,triglyceride,low density lipoprotein cholesterol and classification of OSAHS were independent predictors for cardiovascular composite endpoint events. Conclusion Moderate and severe OSAHS is related to the severity of coronary artery lesions in patients with ACS.Complicated OSAHS in patients with ACS may increase the incidence rate of cardiovascular composite endpoint events,especially severe OSAHS.OSAHS is an independent predictor for cardiovascular composite endpoint events in patients with ACS.