AIM: To study immunosuppressive effects of Tongbizhitong Capsule. To reveal the anti-inflammatory mechanism of this capsule. METHODS : The anti-inflammatory effect was determined with the adjuvant arthritis models of the rats with adjuvant arthris (AA) paw edema. We also observed the blood oxygen free radican,nitric oxide(NO) with AA. The immunosuppressive effect was determined with T-cell subsets in spleen of rats with AA,serum haemolysin level of mouse,the delayed type hypersensitivity. RESULTS : Tongbizhitong Capsule had remarkable inhibitory effect on carrageenine induced granulation and on the prevention of AA. In the T-cell subsets: low,middle and high dose decreased T_h and high dose inhibited both T_s and T_h preacted mainly on T_h and rendered the decreased ratio of T_h/T_s. The delayed type hypersensitivity reaction was distinctly suppressed. It also had a suppressive action on serum haemolsin. Only the high dose could decrease serum lipid deroxides and NO contents,and increase superoxide dismutase and glutathione peroxidase levels. CONCLUSION : Tongbizhitong Capsule has suppressive effect on immune function.