Abstract: Objective: To observe the influence of soybean isoflavone(SI) on the lipid peroxidation in Wistar rats.Methods: Fifty Wistar rats were randomly divided into five groups and fed on foundation feed,high fat feed and high fat feed mixed with 30 mg/kg,90 mg/kg and 270 mg/kg SI respectively.The experiment lasted for 7 weeks.Results: SI at low dose level had preventive effect on the rise of lipid peroxidation induced by high fat feed(P<0.01),but SI at high dose level did not(P>0.05).experiment groups had lower level of NO in the serum and higher level in the tissue than the control(P<0.05~P<0.01).Conclusions: SI can improve the abnormal oxidation caused by high fat feed,alleviate the lesion due to peroxidation,and influence the NO level in the serum.