Objective To explore the effects of one time loading of different doses of simvastatin before percutaneous coronary intervention (PCI)on post-PCI inflammation,oxidation stress and the endothelium function in (ACS) patients. Methods Totally 124 cases with ACS were randomly divided into two groups:high dose simvastatin group(40 mg,62 cases),low dose simvastatin group (20 mg,62 cases). Each group was given the same basic treatment. Blood samples were obtained from all the patients before and 12 h after PCI,and endothelin-1 (ET-1),nitric oxide (NO),interleukin-10(IL-10),high sensitive - C reactive protein(hs-CRP),superoxide dismutase (SOD) and malondialdehyde(MDA) were detected. Results The baseline information,distribution of sex,age,and implanted frames had no significant differences between the two groups (P＞0.05).Before PCI,the levels of ET-1,NO,IL-10,hs-CRP,SOD and MDA had no significant differences (P＞0.05) between the two groups.After PCI,ET-1,IL-10 and hs-CRP levels in simvastatin 40 mg group were significant lower while NO level was higher than in simvastatin 20 mg group[(4.4 ± 1.1)ng/L vs.(4.8±1.2)ng/L,t=2.03,P=0.044; (15.0±6.3) ng/L vs.(18.7±9.0)ng/L,t=2.68,P=0.008;(26.9±10.0)ng/L vs.(31.5± 11.7)ng/L,t=2.52,P =0.022;(51.9± 10.9)μmol/L vs.(47.1±11.8)μmol/L,t=2.37,P=0.020].There were no significant differences in MDA and SOD levels between the two groups.For safety,all the patients had no abnormality in liver and kidney function after treatment. Conclusions Compared with 20 mg simvastatin loading before PCI,the 40mg simvastatin loading may decrease the inflammatory cytokines and improve the endothelium function more effectively.