CIA models were duplicated by SD rats using bovine collagen type 2, then rats were divided into control group, CIA group, baicalin group(50mg ·kg^-1 · d^-1) and methotrexate group(0.9 mg · kg^-1· w^-1) randomly. Rats in each gourp recieve appropriate drug ad- ministration. The rats were sacrificed after 35 days administration, joints slice were made to get HE staining and immunohistochemi- cal staining. The pathological changes of the cartilage and bone were observed and inflammatory cytokines TNF-alpha, IL-17, PGE2 expression on cartil...