Acute coronary syndrome(ACS) is one of the most common cardiology intensive diseases.The percutaneous coronary intervention(PCI),especially the emergency or elective PCI is an important treatment.The application of anti- platelet aggregation drugs before and after the treatment is very important,but the incidence of thrombocytopenia(GIT) induced by platelet glycoprotein Ⅱb / Ⅲa receptor antagonist(for instance,tirofiban) can increase significantly.This article reports a case of PCI patients had no thrombocytopenia after the first application of tirofiban,but the tirofiban lead to severe thrombocytopenia after the application of tirofiban again after the second PCI because of subacute stent thrombosis.The study of this case and other literatures from other countries indicate that close attention should be paid to tirofiban- induced thrombocytopenia.