Objective: To explore the effect and safety of pre-operative loading ticagrelor on myocardium reperfusion in patients with acute ST-elevation myocardial infarction (STEMI) during primary percutaneous coronary intervention (PCI). Methods: A total of 105 acute STEMI patients received PCI within 12-hour of onset were studied and they were divided into 2 groups: Ticagrelor group, the patients received pre-operative oral chewing ticagrelor 180 mg,n=58 and Clopidogrel group, the patients received pre-operative oral chewing clopidogrel 600 mg,n=47. The baseline feathers, operative TIMI and corrected TIMI frame count (CTFC), TIMI myocardial perfusion grade (TMPG), no-relfow/slow lfow conditions were compared between 2 groups. Results: The baseline feathers and pre-operative TIMI were similar between 2 groups, bothP>0.05. Compared with Clopidogrel group, Ticagrelor group showed increased ratios of TIMI 3 lfow (94.8% vs 80.9%) and TMPG (89.7% vs 72.3%), bothP<0.05, improved CTFC (20.0 ± 4.9) vs (31.8 ± 3.9),P<0.001; decreased rates of no-relfow/slow lfow,P=0.016 and less MACE occurrence,P<0.05; while the post-operative bleeding events were similar between 2 groups,P>0.05. Conclusion: Prior PCI loading ticagrelor may reduce no-relfow/slow lfow incidence, improve myocardium reperfusion safely and therefore, decrease MACE occurrence in acute STEMI patients.