Abstract: AIM To investigate the correlation between the distribution of description CYP2C19 polymorphism and its role in anti-platelet therapy in patients with acute coronary syndrome after percutaneous coronary intervention (PCI). METHODSA total of 2117 patients diagnosed as having coronary atherosclerotic heart diseases in Xijing Hospital were selected and gene polymophisms were analyzed. Based on the loss of function allele gene, the cases were divided into three genotypes: fast metabolic genotype (*1/*1), intermediate metabolic genotype (*1/*2, *1/*3) and slow metabolic genotype (*2/ *2, *2/*3, *3/*3). Eight hundred and sixty-four cases with complete clinical data from the 2117 cases were divided into normal metabolic group (fast metabolic genotype, n=346) and poor metabolic group (intermediate metabolic genotype and slow metabolic genotype, n=461) and received anti-platelet therapy. Major adverse cardiovascular events (MACE) were recorded and compared 1, 3, 6, 9 and 12 months post-PCI between two groups. RESULTSAccording to gene type, 885 cases (41.80%) were fast metabolic genotype, 971 cases (45.86%) were intermediary metabolism genotype and 261 cases (12.32%) were slow metabolic genotype. Loss of follow-up was 36 cases and 21 cases, respectively, in normal metabolic group and poor metabolic group. For the effect of anti-platelet therapy, no statistically significant difference was observed in the incidence of MACE between normal metabolic group and poor metabolic group. CONCLUSIONThe frequency of CYP2C19 allele mutation is high and mainly genotype *1/*2 in patients after PCI. There is no statistically significant difference in the incidence of MACE between normal metabolic group and poor metabolic group. Post-PCI anti-platelet therapy based on genotype may increase effectiveness.