Abstract: AIM: To explore the effectiveness and safety of simvastatin in the treatment of ortholiposis acute coronary syndrome (ACS). METHODS: Two hundred and thirty-nine ACS patients were randomly divided into treatment group (n=115) and control group (n=124), and an additional 20 mg/day simvastatin was administered orally in the treatment group in addition to the same normal treatment of the control group. Patients in the treatment group continued to take simvastatin orally for 6 months after hospital discharge and follow-up visits were done for all patients. The incidence rates of major cardiovascular events of the two groups before and after taking simvastatin were observed. RESULTS: Eighteen cardiovascular events (15.65%) were found in the treatment group after taking simvastatin for 6 months, whereas 49 cardiovascular events (39.52%) were found in the control group, with significant difference between groups (P<0.05). Total cholesterol (TC) in serum, low-density lipoprotein cholesterol (LDL-C) and C-reactive protein (CRP) after treatment were significantly lower than those before treatment (P<0.05). No significant difference was found in adverse reactions between groups (P>0.05). CONCLUSION: Simvastatin is effective and safe in the treatment of ortholiposis ACS.