OBJECTIVE： To explore the improvement effect of different polar parts of Sanye Chongcha on models rat with ulcerative colitis （UC）. METHODS： The total extract was obtained from Sanye Chongcha by extraction with 80％ ethanol， and dispersed in water， from which the extracts of corresponding parts were obtained after extraction successively with trichloromethane and ethyl acetate and drying. 60 rats were randomized into normal group， model group， positive group （sulfasalazine enteric-coated tablets， 312.5 mg/kg）， trichloromethane extraction part group （70 mg/kg）， ethyl acetate extraction part group （35 mg/kg） and water extraction part group （320 mg/kg）. The rats except for normal group received 2，4，6-trinitrobenzenesulfonic acid solution （TNBS） to establish UC model. 24 h later， the rats in the drug administration groups were given corresponding drugs ig， while those in normal group and model group were given normal saline ig， once a day， for 14 consecutive days. For the rats， the pathological change of the colon tissue was observed， and the colon mucosa damage index （CMDI） was scored； the activity of superoxide dismutase （SOD） and the content of malondialdehyde （MDA） in serum were determined. RESULTS： Compared to normal group， the rats in model group had obvious UC-like lesion， higher CMDI， lower activity of SOD and higher content of MDA in serum （P＜0.01）. Compared to model group， the rats in the drug administration groups had the lesion which became less serious or improved and had lower CMDI score， among which those of the ethyl acetate extraction part group and the positive group demonstrated a statistically significant difference （P＜0.01）； and the rats in the drug administration groups except for trichloromethane extraction part group had higher activity of SOD and lower content of MDA in serum， among which the activity of SOD of the ethyl acetate extraction part group and the activity of SOD and content of MDA of the positive group demonstrated a statistically significant difference （P＜0.05 or P＜0.01）. CONCLUSIONS： The ethyl acetate extraction part of Sanye Chongcha can reduce colonic lipid peroxidation and thus has obvious improvement effect on the rats with UC caused by TNBS.