To screen an optimal ulcerative colitis animal model more close to the pathogenesis of human body by analysis of the strength and weakness between the immune complex method and the chemical method for establishing an experimental rat model. Methods: Wistar rats were randomly divided into normal group, immune complex group and chemical group. Rats in immune complex group are injected with antigen emulsion (including 8 mg variant antigen) once a week in the first three weeks. In the fourth week, the rats in the immune complex group and those in the chemical group were coloclystered by TNBS (2, 4, 6-trinitrobenzenesulfonic acid sol, 100 mg/kg) and 50% alcohol. Colon samples from the three groups were taken at the 1 st, 14th and 56th day respectively and symptom, sign and pathological reaction of the three groups after modeling were compared. Results: Compared with the normal group, rats in the immune complex group and chemical group had typical ulcerative colitis symptoms at the 1 st day, like loose stool, ulcer, inflammatory reaction, while the submucosa inflammatory reaction of rats in the immune complex group was stronger than that of the chemical group lasting for eight weeks. The ulcer in the chemical group was more severe than that of the immune complex group, but submucosa inflammatory reaction weaker, with less duration and self-cures two weeks later. Conclusion: The immune complex model is the optical ulcerative colitis one, for stable performance, easily repeated, and long duration and the ulcerative colitis pathogenesis in rat model is much more close to that of human body.