This study was designed to investigate the therapeutic effect of sodium formononetin-3'-sulphonate (Sul-F), a water-soluble derivate of formononetin, on acute myocardial infarction in rats. The results showed that treatment with Sul-F significantly prevented the elevation of ST-segment level, decreased the contents of creatine kinase-MB, lactate dehydrogenase, alanine aminotransferase and cardiac troponin T in serum and reduced the myocardium necrosis scores. The number of apoptosis cardiocytes is well accordance with the up-regulated expression of Bcl-2 and the down-regulated expression of Bax. Meanwhile, Sul-F significantly increased the cardiac mitochondrial ATP content, improved ATP synthase activity, decreased thiobarbituric acid-reactive substances content and attenuated the decrease in superoxide dismutase and glutathione peroxidase activities. These findings indicate that Sul-F has a protective potential against myocardial infarction injury. A possible mechanism for the protective effect is the elevated expression of endogenous antioxidant defence enzymes degraded lipid peroxidation products and improved energy metholism of cardiac mitochondrial, thus attenuating cardiocyte apoptosis.