Abstract: Objective To investigate the relationship between plasma cytochrome P450 3A4 (CYP3A4) 894C>T gene polymorphism and the risk of recurrence of adverse cardiac events after percutaneous coronary intervention (PCI) in patients with acute coronary syndrome (ACS). Methods A total of 275 patients with ACS received standard dual antiplatelet therapy and PCI. Platelet aggregation rate (PAR) was detected in each patient before and 7 days after administration of the anti-platelet drugs. Single nucleotide polymorphism of CYP3A4 gene 894C>T was detected with PCR and microarray technique. The number of coronary artery lesions was determined by PCI and the Gensini score was calculated. The patients were followed up for 3-12 months after discharge. Results No significant difference was found in CYP3A4 gene polymorphism between patients with clopidogrel resistance (CR group) and those without CR (NCR group) (P>0.05). Multivariate logistic regression analysis showed that CYP3A4 gene 894C>T polymorphism was not correlated with CR in patients with ACS (OR 1.359, P>0.05). During the follow-up, the incidence of cardiovascular events was significantly higher in CR group than in NCR group (P<0.05), but this difference was not related to the mutation type of 894C>T locus of CYP3A4 gene. Conclusion The CYP3A4 gene 894C>T polymorphism is not associated with the effect of anti-platelet therapy and the risk of cardiovascular event in patients with ACS following PCI.