Abstract: AIM To evaluate the safety and efficacy of GPⅡb/Ⅲa receptor antagonists intracoronary tirofiban injection in patients with acute STsegment elevation myocardial infarction (STEMI) before primary PCI. METHODS Sixtyseven acute STEMI patients (48 men and 19 women, aged 57±8 years old) with TAR thrombolysis during CAG from the past 2 years were divided into two groups: intracoronary tirofiban injection＋PCI group (n=35) and primary PCI group (n=32). TIMI flow during operation, post operation cardiac function (left ventricular ejection fraction), major adverse cardiovascular events (MACE) rates and bleeding state in hospital were compared between the two groups. RESULTS The rates of noreflow and arrhyehmia in intracoronary tirofiban injection＋PCI group were lower than that in primary PCI group（3％ vs 19％, 3% vs 16%, P<0.05） and so was the major adverse cardiovascular events (MACE) rates (3% vs 9％). Post operation cardiac function (LVEF) of intracoronary tirofiban injection＋PCI group was better than that in primary PCI group［（57±5）％ vs (51±10)％, P<0.05］ and no difference was found in severe hemorrhage between the two groups. CONCLUSION Intracoronary tirofiban injection before primary PCI in patients with STMEI is safe and effective.