Abstract: OBJECTIVE To study the protective effect of total flavonoids of Gossampim Flos(TFG) on myocardial ischemia and reperfusion injury in rats, and to explore its mechanism. METHODS Healthy SD rats were divided into six groups randomly, 10 rats in each group:sham operation group, model group, positive control group(composite salviae dropping pill 135 mg·kg^-1), TFG low-dose, middle-dose and high-dose group(100, 200, 400 mg·kg^-1), respectively. Except the sham operation group and model group, the rest of the groups were administrated with drugs by ig for 7 days, and once a day, the sham group and the model group were given normal saline. Myocardial ischemia reperfusion injury model was established by anterior descending branch of coronary artery. The activity of CK-MB, CK, LDH and LDH-1 in serum were measured, the levels of SOD, GSH, GSH-Px, NOS and the content of MDA, NO were detected, and myocardial infarct size was assessed by TTC staining, the myocardial tissue lesion was observed by histopathology. RESULTS Compared with the sham operation group, the serum levels of CK-MB, CK, LDH, LDH-1 and MDA were significantly increased in the model group, the activity of SOD, GSH, GSH-Px, NO and NOS in serum of rats in the model group was significantly reduced, myocardial tissue cells were severely infarcted and necrotic. Compared with model group, TFG could significantly reduce the serum contents of CK-MB, CK, LDH, LDH-1 and MDA in rats in each dose group, and could improve the activity of SOD, GSH, GSH-Px, NO and NOS, at the same time, the myocardial infarction area could be reduced, the light microscopic myocardial tissue edema levels and inflammatory cell infiltration were significantly lightened. CONCLUSION TFG shows remarkable protective effects on myocardial ischemia and reperfusion injury in rats, the mechanism may be related to reducing the production of oxygen free radicals and regulating oxidation and antioxidant balance.