OBJECTIVE： To observe the effects of preoperative application of tirofiban on related indexes of patients with acute myocardial infarction. METHODS： In retrospective analysis， 128 patients with acute myocardial infarction selected from our hospital during Jan. 2015-Jun. 2016 were divided into observation group （76 cases） and control group （52 cases） according to whether or not the tirofiban was used before PCI. Control group was given Aspirin enteric-coated tablets 300 mg， po+ Clopidogrel sulfate tablets 600 mg， po， before PCI， and given Heparin sodium injection 100 U/kg ， iv， during PCI. Observation group was additionally given Tirofiban hydrochloride injection 0.2 μg/（kg·min），iv，before PCI，on the basis of control group. ST-segment depression and chest pain remission of 2 groups were observed after PCI. CK-MB level before surgery， CK-MB peak value， the time of CK-MB reaching the peak value， duration after surgery as well as TIMI blood flow grading after surgery were also observed in 2 groups. The levels of von Willebrand factor （vWF）， ET-1 and NO were observed before and after surgery； the occurrence of ADR was recorded. RESULTS： After PCI， ST-segment depression rate （89.74％） of observation group was significantly higher than that （67.31％） of control group， the chest pain remission rate （89.47％） was significantly higher than that of control group （75.00％）， the patients with TIMI blood flow grading grade 2-3 in observation group was more than control group， with statistical significance （P＜0.05）. Before PCI， there was no statistical significance in the levels of CK-MB， vWF， ET-1 and NO between 2 groups （P＞0.05）. After PCI， CK-MB peak value， the time of CK-MB reaching the peak value， duration in observation group were significantly lower or shorter than control group； the levels of vWF and ET-1 significantly decreased， while NO levels increased； the improvement of vWF， ET-1 and NO in observation group was significantly better than control group， with statistical significance （P＜0.05）. The incidence of mild bleeding in observation group was significantly lower than control group， while the incidence of moderate bleeding was significantly higher than control group， with statistical significance （P＜0.05）. There was no statistical significance in the incidence of death between 2 groups （P＞0.05）. CONCLUSIONS： The application of tirofiban before PCI can relieve clinical symptom， improve cardiac function， protect vascular endothelial and restore coronary artery perfusion. The attention should be paid to the risk of bleeding.