Abstract: [ Objective ]The research aimed to study the inhibition and inhibitory mechanism of forsythiaside A against rheumatiod arthritis of rat. [ Method ] Thirty SD rats with the weight of （120±2） g were randomly divided into three groups with 10 rats in each group： control group （A group）, rheumatiod arthritis group （B group） and forsythiaside A therapy group （C group）. The rheumatoid arthritis rat model was constructed to observe the clinical symptoms of rats, the expression amount of TNF-α protein in the serum, antioxidase and free radicals contents in each group. [Result] The expression amount of TNF-α protein in the serum of rats increased in rheumatoid arthritis model group, SOD content decreased and NO content increased. The trends of the above indices were on the contrary in forsythiaside A therapy group. [Conclusion ] Forsythiaside A could affect the contents of TNF-α protein and free radicals by inhibiting the content of TNF-α of inflammatory factor, and interferential the translation of TNF-α protein, eventually the anti-inflammatory effect was obtained.