OBJECTIVE： To explore the repairing effect and mechanism of Huazhuo jiedu yukui formula on the mucosal damage of rats with ulcerative colitis （UC）. METHODS： 72 rats were randomly divided into blank group， model group， mesalamine group （positive control， 0.3 g/kg）， Huazhuo jiedu yukui formula low-dose， medium-dose， high-dose groups （5， 10， 20 g/kg）， 12 in each group. Except for blank group， other groups were induced UC model. After 4 d of modeling， rats in administration groups received related medicines， ig， blank group and model group received normal saline， ig， once a day， for 2 weeks. After administration， disease activity index （DAI） and mucosal damage index （CMDI） of rats were observed； IL-8， TNF-α contents in serum and cyclooxygenase 2 （COX-2） expression in colon tissue were detected. RESULTS： Compared with blank group， DAI and CMDI scores in model group were increased； IL-8， TNF-α contents in serum were increased； COX-2 expression in colon tissue was enhanced， with statistical significances （P＜0.05）. Compared with model group， DAI and CMDI scores in model group were decreased； IL-8， TNF-α contents in serum were reduced； COX-2 expression in colon tissue was weakened， with statistical significances （P＜0.05）. Compared with mesalamine group， the above-mentioned indicators in Huazhuo jiedu yukui formula medium-dose， high-dose groups changed more obviously （P＜0.05）， and effects of Huazhuo jiedu yukui formula showed significant dose-effect relationship. CONCLUSIONS： Huazhuo jiedu yukui formula can improve disease activity status of UC rats and reduce colon mucosal damage， and the effects of medium-dose and high-dose Huazhuo jiedu yukui formula were better than mesalamine， which may be related to reducing inflammatory reaction and inhibiting COX-2 expression in colon tissue.