OBJECTIVE： To compare clinical efficacy of bivalirudin vs. tirofiban combined with heparin in the treatment of acute ST elevation myocardial infarction （STEMI） complicated with diabetes mellitus （DM）. METHODS： 195 patients diagnosed as STEMI complicated with DM were selected for retrospective study， and divided into bivalirudin group （100 cases） and tirofiban group （95 cases） according to the different treatment plan. All patients received emergency PCI within 12 hours and conventionally took aspirin and clopidogrel before and after PCI. Bivalirudin group was given bivalirudin 0.75 mg/kg intravenously before PCI， and continuous intravenous dripping of 1.75 mg/（kg·h） till the end of operation. Tirofiban group was given heparin 100 U/kg and tirofiban 10 μg/kg intravenously before PCI， and continuous intravenous dripping of 0.75 μg/（kg·h） tirofiban for 36 h. Postoperative reperfusion indexes， UCG monitoring indexes and safety were compared between 2 groups， and the content of serum BNP were compared before and after treatment. RESULTS： For the TIMI grade， TIMI frame count， the peak of CK-MB and peak time， ST segment decline percentage immediately after PCI， contents of serum BNP， LVEF， LVESD， LVEDD 7， 30 d after treatment， the differences were not statistically significant between 2 groups （P＞0.05）. The incidence of MACE events was 36.8％ in tirofiban group and 41.0％ in bivalirudin group， there was no statistical significance between 2 groups （P＞0.05）. The incidence of bleeding events was 24.2％ in tirofiban group and 7.0％ in bivalirudin group， the difference was statistically significant （P＜0.05）.  CONCLUSIONS： Bivalirudin and tirofiban combining with heparin have same efficacy in the treatment of STEMI complicated with DM， while bivalirudin may significantly reduce the incidence of bleeding events during primary PCI.