【Abstract】Objective To study the effects of sequential therapy with ticagrelor and clopidogrel on microvascular injury and CRP level in patients with acute STsegment elevation myocardial infarction (STEMI) during emergency percutaneous coronary intervention (PCI). Methods 112 STEMI patients scheduled to undergo emergency PCI in our hospital from April 2015 to April 2018 were selected and randomly divided into observation group and control group, with 56 cases in each group. The two groups were given routine emergency PCI after entering the group. The control group was treated with clopidogrel, and observation group was given sequential therapy with ticagrelor and clopidogrel. The postoperative microcirculation resistance index (IMR), coronary flow reserve (CFR) and fractional flow reserve (FFR) were observed in the two groups. The platelet aggregation rate and Creactive protein (CRP) level were recorded before operation and at 2h, 24h, 7d and 30d after operation, and the incidence rates of adverse cardiovascular and hemorrhagic events within 30d after operation were counted. Results The postoperative IMR value in observation group was lower than that in control group (P＜005), and the CFR and FFR values in the two groups were equivalent (P＞005). There were significant differences in platelet aggregation rate and CRP level between the two groups (P＜005), and the platelet aggregation rate and CRP level in observation group were lower than those in control group at each time period after operation (P＜005). The incidence rate of vascular adverse events in observation group within 30d after operation was lower than that in control group (714% vs 2321%) (P＞005). The incidence rate of hemorrhagic events in observation group within 30d after operation was equivalent to that in control group (893% vs 536%) (P＞005). ConclusionSequential therapy with ticagrelor and clopidogrel in STEMI patients during emergency PCI can reduce microvascular injury, inhibit coronary vascular inflammatory response and platelet aggregation, improve cardiac function and reduce the incidence of vascular adverse events within 30d.