Objective To study the effects of modified Buyang Huanwu decoction on adjuvant-induced arthritis,and the mechanism of this decoction in treating rheumatoid arthritis. Methods Adjuvant-induced arthritis(AA) model was induced by plantar injection of Freundis complete adjuvant and Observed the level of interlinkin-1(IL-1),tumor necrosis factor-α(TNF-α),circulating immunecomplexes(CIC),malondialdehyde(MDA) and antioxidizing activity of superoxide dismutase(SOD)in AA rats treated with the decoction.Results The contents of IL-1,TNF-α,CIC,MDA obviously decreased and the activity of SOD was increased by Buyan Huanwu Decoction(P＜0.01)in AA rats.Conclusion Modified Buyang Huanwu decoction shows visibly anti-inflammatory function on AA rats,which is associated with its mechanism of suppressing free radical injure and modifying autoimmune physiological and pathological reaction.