OBJECTIVE：To explore the incidence and possible risk factors of clopidogrel resistance in patients of dual antiplatelet treatment with acute coronary syndrome （ACS） after percutaneous coronary intervention （PCI）. METHODS： A total of 93 ACS inpatients with dual antiplatelet drugs who underwent PCI （100 mg/d aspirin and 75 mg/d clopidogrel were given for more than 5 d before surgery， or loading dose of 300 mg aspirin and 300 mg clopidogrel 6 h before surgery， and loading dose of 100 mg/d aspirin and 75 mg/d clopidogrel were given after surgery） were enrolled， thromboelastography（TEG） was used to determine the platelet inhibition rate after giving clopidogrel，patients were divided into resistance group and non-resistance group based on the inhibition rate， and a related risk factors analysis was conducted for clopidogrel resistance. RESULTS：The incidence of clopidogrel resistance was 33.3％ （31 cases）. The total stent lengths and MAADP of clopidogrel resistance group were higher than non-clopidogrel resistance group，the difference was statistically significant（P≤0.01）. CONCLUSIONS： In the ACS patients with dual antiplatelet drugs who underwent PCI， 33.3％ show clopidogrel resistance. Total stent lengths and MAADP are the risk factors of clopidogrel resistance in ACS patients after PCI.