Abstract: Objective: To observe the protective effect of soybean isoflavones(SI) on adriamycin(ADR) induced heart failue in rats.Methods: Twenty four adult male SD rats were divided into 3 groups:normal contrasted(NC)group,ADR group and SI group.SI 120 mg·kg^-1·d^-1 was administered using a stomach tube in SI group once a day for 6 days.The other two groups were given the same amount of normal saline(NS).At day 7,ADR 10 mg/kg was given intraperitoneally(ip) at one time to copy the model of heart failure rats.The LVSP of the rats was recorded,observed and analyzed using the MedLab U/4c biological signal collecting system.Results: Compared with NC group,the LVSP,±dp/dt_max and Vpm of ADR group decreased significantly (P<0.05 to P< 0.01);but the LVSP,±dp/dt_max and Vpm of SI group increased significantly(P<0.05 to P<0.01) compared with those of ADR group.Conclusions: SI can relieve the toxic effect of ADR on myocardiam and greatly improve the contractivity of heart failure in rats.