Abstract: 【Abstract】 Objective To study the effects of dihydroartemisinin on collagen-induced arthritis (CIA) in rats model.Methods CIA was induced in Male Wistar rats by intradermal injection of emulsion of 0.3 mg type Ⅱ collagen in Freund’s completead juvant (CⅡ/FA) at the base of the tail and repeated one times after 15 days. The normal control rats received the injection of the same volume of saline 52 days later, the CIA rats were divided into dihydroartemisinin treated group, saline treated group, in which the rats were subjected to the treatment of dihydroartemisinin 30 mg/(kg·d) or the same volume of saline for 28 days, then the effects of the treatments on arthritis were evaluated..Results Compared with the normal rats, the joints of non-treated CIA rats were obviously swollen. After the treatment of dihydroartemisinin, the joints of CIA rats appeared less inflammation cell erosion, less proliferation of fibrous connective tissue and blood capillary, more clear, articular cavity and no bone erosion. Conclusion This preliminary study indicated dihydroartemisinin may have the effects to relieve CIA in rats.