Rheumatoid arthritis (RA) is a chronic autoimmunity disease which shows synovitis.The activity of SOD in RA patient is reduced,which attenuated the ability to clear free radical.We performed animal experiments to test the effect of the superoxide dismutase (SOD) and the fusion protein (PTD-SOD) consisting of a SOD linked to a protein transducfion domain (TAT) in RA treatment.The experimented animal model of adjuvant arthritis rats was established by injection of complete Freunds adjuvant at ankle site.Pour normal saline,SOD or PTD-SOD into stomach respectively to different group.