Abstract: Objective To investigate the protective effects of Shengmaisan on myocardial injury induced by endogenous and exogenous free radical in isolated rathearts.Methods The experiment was accomplished by serum pharmacology.All rabbits were treated with Shengmaisan viagastric gavage twice daily for three days consecutively.After this treatment,60 min after the last dosing the blood was taken and the serum was separated.The herbal medicines serum was added to the isolated rathearts perfused in a Langendorff model.Left ventricular pressure(LVP),the frist derivative of LVP(+dp/dtmax),left ventricular end-diastolic pressure(LVEDP)and heart rate(HR)were recorded.Coronary flow(CF)in coronary effluent were measured by timed collection of coronary effluent,at the end of the reperfusion,the content of malondialdahycle(MDA)in cardiac tissue was measured.Results Perfusion with1,1-diphenyl-2-picryl-hydrazyl(DPPH 0.25μmol/L)or hypoxanthine (HX 0.06μmol/L)and xanthine oxidase(XO 2.0 μ/L)for 10 min caused a marked decrease in LVP and+dp/dtmax,and an increase in LVEDP,the release of CK and the content of MDA.pretreatment with herbal medicines serum for 10 min produced a significant improvement of cardiac function injury induced by DPPH or HX+XO and a decrease in the release of CK and the content of MDA.Conclusion Shengmaisan marked protectively effects on myocardiac injury induced by endogenous and exogenous free radical which were produced by DPPH or HX+XO.