This was a single-center, randomized, prospective study. ACS patients undergoing PCI treated with clopidogrel and aspirin were included. in the 3-5th day after prescription of clopidogrel, platelet function were tested simultaneously by three methods: MPAADP by Light transmittance aggregometry（LTA）, MAADP by Thrombelastography (TEG) ,and CTP2Y by Innovance PFA-200 . According to three result（Two of three or all three results higher than cutoff value was identified as HPR, MPALTA>50%;MAADP>47mm;CTP2Y<106s）.Patients was defined as HPR(n=125) or unHPR(n=232), HPR patients were divided into HPR-Ticagrelor(HPR-T)and HPR-Clopidogrel(HPR-C) randomized. HPR-T group(n=77) patients' antiplatelet agents changed to ticagrelor, both unHPR and HPR-C groups keep unchanged(Clopidogrel). The major adverse cardiovascular events (MACE) were recorded during 1 year Follow-up.