Aim To study the effect and possible mechanism of mangiferin on myocardial ischemia reperfusion (MIR) injury in rats. Methods Fouty-eight SD rats were randomly divided into six groups: sham group, model group, mangiferin groups of 10 mg/kg, 20 mg/kg, 40 mg/kg and Diaoxinxuekang group. Each group were injected with corresponding concentrations of mangferin, Diaoxin xuekang or equal volume of saline gastrogavaged for 21 d. 0ne hour after the last administration myocardial ischemia reperfusion models were obtained by ligated left anterior descending coronary artery 40 minutes and followed by 120 minutes reperfusion and sham group was given all the procedures except ligation. Ultrastructure of myocardium with TEM and infiltration of polymorpho nuclear neutrophils (PMN) in myocardium with myeloperoxidase (MPO) were observed; serum activity of lactate dehyd -rogease (LDH), myocardial activity of superox -ide dismutase (SOD) and contents of malondialdehyde (MDA) were detected respectively. Results Mangiferin could improve myocardial pathology and ultrastructurein mangiferin 10 mg/kg group the activities of SOD was higher (P<0.05); the contents of MPO, MDA, LDH were significantly lower (P<0.05). Conclusion Mangiferin can protect MIR. The myocardial protective mechanism of it may be realized by enhancing the activation of SOD activity,enhancing myocardial antioxygen capability, stabilizing myocardial cellular membrance and alleviating infiltration of polymerrphonuclear neutrophils(PMN) in myocardium.