Background:There was still conflict on the antithrombotic advantage of ticagrelor versus clopidogrel among East Asian population with acute coronary syndrome (ACS).We considered that the baseline bleeding risk might be an undetected key factor that significantly affected the efficacy of ticagrelor.Methods:A total of 20,816 serial patients who underwent percutaneous coronary intervention (PC I) from October 2011 to August 2014 in the General Hospital of Shenyang Military Region were enrolled in the present study.Patients receiving ticagrelor or clopidogrel were further subdivided according to basic bleeding risk.The primary outcome was net adverse clinical events (NACEs) defined as major adverse cardiac or cerebral events (MACCE,including all-cause death,myocardial infarction,ischemia-driven target vessel revascularization,or stroke) and any bleeding during l-year follow-up.Comparison between ticagrelor and clopidogrel was adjusted by propensity score matching (PSM).Results:Among the 20,816 eligible PCI patients who were included in this study,there were 1578 and 779 patients in the clopidogrel and ticagrelor groups,respectively,after PSM,their clinical parameters were well matched.Patients receiving ticagrelor showed comparable NACE risk compared with those treated by clopidogrel (5.3％ vs.5.1％,P=0.842).Furthermore,ticagrelor might reduce the MACCE risk in patients with low bleeding risk but increase MACCE in patients with moderate-to-high bleeding potential (ticagrelor vs.clopidogrel,low bleeding risk:2.5％ vs.4.9％,P =0.022;moderate-to-high bleeding risk:4.8％ vs.3.0％,P =0.225;interaction P =0.021),with vast differences in all bleeding (low bleeding risk:1.5％ vs.0.8％,P =0.210;moderate-to-high bleeding risk:4.8％ vs.3.0％,P=0.002;interaction P =0.296).Conclusion:Among real-world Chinese patients with ACS treated by PCI,ticagrelor only showed superior efficacy in patients with low bleeding risk but lost its advantage in patients with moderate-to-high bleeding potential.