Kursi Caper (KC) is a Uighur medicine based on caper which is widely used to treat arthritis and rheumatism, and preliminary studies in our laboratory showed that this traditional formula may possess potent antiinflammatory effects. This study confirms the antiinflammatory effect of KC in the adjuvant induced arthritis (AIA) model, the carrageenan and cotton-pellet induced granuloma rat models, and further investigates in vivo the mechanism of action by measuring relevant indicators of anti-arthritic activity. KC showed significant and dose-dependent anti-arthritic and antiinflammatory effects, demonstrated by reduced paw edema and arthritic scores in all animal models. Histopathological examination showed that KC reduced levels of synovial inflammatory factors in AIA rats. The overproduction of TNF-alpha and IL-1 beta was attenuated, and CAT, MDA and SOD levels were restored to normal in KC-treated rats. KC also significantly reduced LPS-induced proliferation of B lymphocytes and ConA induced proliferation of T lymphocytes in a dose-dependent manner. Flow cytometry showed that the high dose KC-treated group had a significantly decreased frequency of Th17 cells. This study indicates that KC can significantly attenuate arthritis and inflammation in rats by decreasing the levels of inflammatory cytokines, regulating oxidative stress, reducing lymphocyte proliferation and decreasing Th17. This supports the traditional use of KC as a potential modern therapeutic agent for the treatment of arthritis and related conditions.