Objective:To observe the therapeutic effect of Guizhi-Shaoyao-Zhimu（GSZ） decoction on imunologic arthritis and investigate the mechanism of this drug on the disease.Methods:Rats were prepared for immunologic arthritis models induced by Freund’s complete adjuvant（FCA）.Different doses of GSZ decoction（20.6 g·kg-1

10.3 g·kg-1） were administrated on the rat model.The counter-lateral synovial tissues of the knee joint were taken for observing pathological changes and the expression of RANKL.Results:In a 4-week of administration of GSZ

lessened swelling of the joints and arthritis index was observed（P<0.05 or P<0.01）.The pathological findings suggested there was less severe inflammation in synovium of the joints and fibrous tissues and decreased infiltrating cells.The RANKL expression in synovial tissues tended to decrease（P<0.01）.Moreover

the findings suggest that GSZ 20.6 g·kg-1 can be favorable with respect to MTX in treatment of immunologic arthritis.Conclusions:GSZ Decoction can protect the joint impairment of immunologic arthritis rats.The therapeutic mechanism maybe is relevant to inhibit inflammation and the expression of RANKL.