AbstractTirofiban is widely used in patients with acute ST elevation myocardial infarction (STEMI) underwent percutaneous coronary intervention (PCI). This drug can efficiently improve myocardial perfusion and cardiac function, but its dose still remains controversial. We here investigated the effects of different dose of tirofiban on myocardial reperfusion and heart function in patients with STEMI. A total of 312 STEMI patients who underwent PCI in our hospital from March 2017 to March 2018 were enrolled and randomly divided into control group (75 cases, 0 μg/kg), low-dose group (79 cases, 5 μg/kg), medium-dose group (81 cases, 10 μg/kg) and high-dose group (77 cases, 20 μg/kg). The infarction-targeted artery flow grade evaluated by thrombolysis in myocardial infarction (TIMI), corrected TIMI frame count (CTFC) and sum-ST-segment resolution were recorded. At Day 7 and Day 30 after PCI, the left ventricular ejection fraction (LVEF), left ventricular end diastolic diameter, left ventricular end systolic diameter, major adverse cardiovascular events and the hemorrhage and thrombocytopenia were also evaluated. After PCI, the rate of TIMI grade 3, CTFC and incidence of sum-ST-segment resolution > 50% of high-dose group were significantly higher than those of control group, low-dose group and medium-dose group (P < .05), and the CTFC of medium -dose group were significantly higher than that of control group, low-dose group (P < .05). Moreover, the LVEF, left ventricular end diastolic diameter and left ventricular end systolic diameter of high-dose group were significantly improved than those of other groups, and the LVEF of medium-dose group was significantly superior to that of low-dose group (P < .05). However, the incidence of major adverse cardiac events in high-dose group was significantly decreased, while the hemorrhage and incidence of thrombocytopenia of high-dose group were significantly higher than those of other 3 groups (P < .05). The tirofiban can effectively alleviate the myocardial ischemia-reperfusion injury and promote the recovery of cardiac function in STEMI patients underwent PCI. Although the high-dose can enhance the clinical effects, it also increased the hemorrhagic risk. Therefore, the rational dosage application of tirofiban become much indispensable in view of patient's conditions and hemorrhagic risk, and a medium dose of 10 μg/kg may be appropriate for patients without high hemorrhagic risk.