Objective To investigate the effect of blood Hcy level on the prognosis of patients with acute ST segment elevation myocardial infarction. Methods 60 patients with acute ST segment elevation myocardial infarction which confirmed by coronary angiography single vascular acute thrombosis were divided into high Hcy group (Hcy ≥ 10 μ mol/L, 33 cases) and normal Hcy group (Hcy<10 μ mol/L, 27 cases) according the Hcy level. Two groups of patients were observed and compared baseline characteristics, and in-hospital mortality and major adverse cardiac events (MACE) rate. Results There were significantly different on baseline levels of BNP and blood pressure between two groups （P<0.05）. High Hcy group in-hospital mortality and incidence of adverse cardiac events was significantly higher than normal Hcy group (P<0.05). Conclusion For patients with acute ST segment elevation myocardial infarction (mi), the prognosis of patients with high Hcy levels is worse than normal Hcy. The levels of plasma Hcy may be an independent prediction index of prognosis in patients with acute myocardial infarction.