Aim To investigate the relationship between nocturnal chest pain and obstructive sleep apnea hypopnea syndrome （OSAHS） in patients with coronary stenosis <50%. Methods 146 inpatients who were suspected to have coronary heart disease （CHD） and complained with snoring in night were selected and divided into two groups （nocturnal chest pain group and control group） according to clinical manifestations. All subjects were performed with coronary angiography and polysomnography （PSG）. The PSG parameters were compared between two groups in patients with coronary stenosis<50%, and the relationship of nocturnal chest pain and OSAHS were discussed. Results 44 patients （30.1%） with coronary stenosis<50% were detected, in whom 5 cases with nocturnal chest pain were diagnosed as moderate or severe OSAHS, all of them combined with moderate or severe hypoxemia in the night. The apnea-hyponea index（AHI） in patients with nocturnal chest pain was significantly higher than that in patients without nocturnal chest pain［（37.14 vs 16.71, P0.04］, as well as the proportion of moderate and severe hypoxia （100% vs 64.1%, P0.04） Adjusting for age, gender and body mass index, Pearson correlation analysis showed that nocturnal chest pain were positively correlated with AHI （r′0.33）, total cholesterol （r′0.40）, low-density lipoprotein cholesterol（r′0.45） and fasting blood glucose （r′0.39）. Conclusion Moderate or severe hypoxemia caused by OSAHS may be associated with nocturnal chest pain patients with coronary stenosis <50%.