Abstract: Objective To investigate the effect of preoperative high d ensity lipoprotein cholesterol(HDL-C)on myocardial ischemia-reperfusion injury(MIRI), major adverse cardiac events(MACE)in hospital and 1 year after primary percutaneous coronary intervention(PCI)in patients with ST-segment elevation myocardial infarction(STEMI)undergoing PCI. Methods One hundred and eighteen patients with STEMI treated with PCI in our hospital from January 2012 to January 2013 were enrolled in this study, with an average age of(60±13)years old and male ratio of 83.1%.The subjects were divided into two groups according to whether the preoperative HDL-C level was normal or abnormal low HDL-C group(n=46): HDL-C＜1.04 mmol/L; high HDL-C group(n=72): HDL-C＞ 1.04 mmol/L.The differences of MACE rates and MIRI status between low group and high group were compared. Results Compared with low group, the differences of the level of total cholesterol and the proportion of patients with Killip grade above or equal toⅢlevel were significant in high group (3.9±1.0)mmol/L vs(4.9±1.0)mmol/L, P＜0.001; 17% vs 1.4%, P=0.001.The remaining baseline features had no significant difference between two groups.Compared with high group, the reperfusion arrhythmia(RA)rate, serum creatine phosphokinase(CK)peak value, serum CK isoenzyme MB(CK-MB)peak value were higher in low group 76% vs 58%, P=0.048; (275±162)U/L vs(212±154)U/L, P=0.035, (3 173±1 905)U/L vs(2 396± 1 994)U/L, P=0.038, but the level of LVEF was lower (51.2±7)% vs(56.3±8)%, P＜0.001.The hospital MACE rate was lower in high group than in low group(28% vs 11%, P=0.018), but there were no significant differences within 1 year MACE rate after PCI between two groups. Conclusion Preoperative high level of HDL-C in patients with STEMI treated by emergency PCI can limit or decrease the incidence of MIRI, and reduce the occurrence of MACE in hospital.