Objective To study the therapeutic effect of New Simiao Formula for rheumatoid arthritis （RA） at active stage and its mechanisms.Methods Totally 60 cases of RA were randomly and equally divided into two groups. New Simiao Formula was used in treatment group

and Xinhuang Tablet in control group. Contrast and observation was done before and after treatment.Results New Simiao Formula could decrease the level of interleukin-1（IL-1）

interleukin-8 （IL-8）

tumor necrosis factor-α （TNF-α）

nitric oxide （NO） and induced nitricoxide synthase （iNOS） obviously

while decrease interleukin-10 （IL-10） obviously. The total effective rates of treatment and control groups were 82.76% and 85.71% respectively

and there was no significant difference between two groups （P>0.05）. The treatment group was superior to control group in relieving arthral symptoms and laboratory indexes （P<0.05）.Conclusion New Simiao Formula is effective for RA at active stage

and resisting the level of IL-1

IL-8

TNF-α

NO and iNOS and increasing the level of IL-10 might be the possible mechanism.