Objective:To study the effects of soybean isoflavone (SI) on metabolism of lipids and lipoprotein (a) [Lp(a)] in ovariectomized rats . Methods:Senventy female Sprague- Dawley (SD) rats were randomly divided into 7 groups according to the levels of total cholesterol (TC) in serum: high-lipid (HF) group, estrogen (EG) group, low-dose SI (L-SI) group, middle-dose SI (M-SI) group, high-dose SI (H-SI) group, sham group and normal control (NC) group. One week after bilateral ovaries were extirpated, except sham and NC group, estrogen, different doses of SI or deionized water were fed i.g. for 12 w. Except NC group, the other groups were fed high fat diet. Body weights were weighed every week and blood and heart were collected at the end of experiment. The serum TC, triglyceride(TG), high or low density lipoprotein-cholesterol (HDL-C, LDL-C), Lp (a), and antioxidative enzymes activities were assayed. Results:After SI intervention, the levels of LDL-C in SI groups were significantly lower than in HF group but higher than in NC group. The levels of Lp (a) were also changed, but there was almost no effect on HDL-C. Persistent intervention with SI can reduce TC, TG , and protect cadiocyte’s actin filament andmitochondrial ultramicrostructure from damage as shown in HF group. The ultramicroscopic pictures in EG and H-SI group almost resembled NC group. Conclusion:Persistent intervention of high-dose SI can reduce the levels of LDL-C, TC, TG and protect the myocardiac damages due to high fat diet in ovariectomized rats.