Abstract: OBJECTIVE To observe possible mechanism of the Qingchang Huashi Fang's therapeutic effect on Ulcerative Colitis(UC)， through observing the expression level of tumor necrosis factor-α(TNF-α) and claudin-1 of mucosal tissue in the experimental colitis rats. METHODS Rats successfully modeled with TNBS/anhydrous alcohol were divided into blank， model， Qichang Huashi Fang(12.8 g crude drug/kg/d) and Mesalazine group(0.67 g/kg/d). Single administration for 10 days successively， all groups of rats were executed to collect colon tissues cut out for related inspections. Using ELISA method to measure the TNF-α concentration of the colon tissues. The expression of claudin-1 protein in colonic epithelium was checked up with immunohistochemical method and relative expression of claudin-1 mRNA with real-time PCR method.RESULTS The TNF-α(pg/mL) concentration of model group and Qichang Huashi Fang group are respectively 99.40±32.37 and 55.07±12.80(P<0.01)；And claudin-1 gene relative expression levels are respectively 2.18±0.78 and 3.94±0.91(P<0.01)；Qichang Huashi decoction can decrease TNF-ａconcentration and increase claudin-1 mRNA relative expression significantly(P<0.01)， thus reducing claudin-1 protein damage(P<0.05). The curative effect between Qichang Huashi Fang and Mesalazine group has no significant difference. CONCLUSION Qichang Huashi Fang can decrease TNF-α concentration and protect tight junction protein claudin-1. That is the one of the mechanisms of Qichang Huashi Fang to treat UC.