Objective? To investigate the correlation between clopidogrel efficacy and CYP2C19 genotype in patients with coronary heart disease after PCI by thromboelastography. Methods? A total of 187 patients with coronary heart disease undergoing PCI admitted to Affiliated Hospital of Qingdao University from January 2017 to January 2019 were selected as study subjects. According to the results of CYP2C19 genotyping and thromboelastic graph ADP inhibition rate detection，they were divided into clopidogre-sensitive group（n=154）and clopidogre-resistant group（n=33）. The levels of MA-ADP and the incidence of cardiac adverse events were compared between the two groups. Results? The inhibition rate of CYP2C19 gene ADP was higher than that of intermediate metabolism type，and that of intermediate metabolism type was higher than that of slow metabolism type（P＜0.05）. The fast metabolism type MA-ADP was lower than the intermediate metabolism type MA-ADP，the intermediate metabolism type was lower than the slow metabolism type MA-ADP（P＜0.05）. The incidence of unstable angina pectoris and acute myocardial infarction in clopidogrel sensitive group was lower than that in clopidogrel resistant group（P＜0.05）. Conclusion ADP inhibition rate and MA-ADP have good correlation with CYP2C19 genotype. Thromboelastography is of great significance in monitoring clopidogrel efficacy and guiding clinical individualized medication in patients with coronary heart disease after PCI.