Abstract: AIM: To investigate the correlation between the distribution of CYP2C19 polymorphisms and the effect of anti-platelet therapy in patients with acute coronary artery disease after percutaneous coronary intervention( PCI). METHODS: We selected 2117 patients diagnosed as having coronary heart disease and treated with PCI in Xijing Hospital. Gene polymorphisms were analyzed in the Han population in northwest China. Based on the loss of functional allele gene,the cases were divided into three gene types: fast metabolic genotypes( * 1 / * 1),intermediate metabolic genotypes( * 1 / * 2,* 1 / * 3) and slow metabolic genotypes( * 2 / * 2,* 2 / * 3 and * 3 / * 3). One hundred and sixty-four cases with complete clinical data from the 2117 cases were divided into normal metabolic group( fast metabolic genotype,n = 59) and poor metabolic group( intermediary metabolism and slow metabolic genotype,n =94) and received anti-platelet therapy. The protocol was as follows: normal metabolism group was given oral clopidogrel 75 mg / d for 1 year and the poor metabolic group was given clopidogrel 150 mg / d of intensive treatment in the first month and 75 mg / d from the second month through the 12 th month. Major adver se cardiac / cerebrovascular events( MACE) incidences were recorded and compared 1,3,6,9 and12 months between groups. RESULTS: According to gene type,885 cases( 41. 80%) were fast metabolic genotype,971 cases( 45. 86%) were intermediate metabolism genotype,and 261 cases( 12. 32%) were slow metabolic genotype. Loss of follow-up was six cases and five cases,respectively,in normal metabolism 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 metabolism group and poor metabolic group. CONCLUSION: The frequency of CYP2C19 allele mutation is high and mainly genotype * 1 / * 2in patients after PCI. There is no statistically significant difference in the incidence of MACE between normal metabolism group and poor metabolic group after different doses of anti-platelet therapy.