Abstract: OBJECTIVE To observe possible mechanism of the Qingchang Huashi Fang's therapeutic effect on Ulcerative Colitis (UC) through regulating Th17/Treg on trinitrobenzene sulfonic acid induced colitis in mice. METHODS Mice successfully modeled with TNBS were divided into blank model， Qingchang Huashi Fang (12.8 crude drug kg/d) and SASP (0.5 g/kg) groups. All Mice， single administration for 7 days， were executed to collect colon tissues and cut out for related inspections. The expression of IL7 and Foxp3 in colonic epithelium was checked up with immunohistochemical method， and measure RORγt and Foxp3 protein in colonic epitheliumand by western blotting method. RESULTS The expression of IL7 in colonic tissues of Qingchang Huashi Fang group were lower than those in blank model group (P<0.05)， and the expression of RORγt protein was significantly lower than those in blank model group (P<0.01). Foxp3 protein was higher than those in model group (P<0.05). CONCLUSION Qingchang Huashi Fang can inhibit Th17 cell differentiation and IL7 generation through lower down egulation RORγt. It can promote Treg cell expression through regulation Foxp3. Qingchang Huashi Fang can effectively inhibit inflammation in TNBS induced colitis in mice through regulation Th17 Treg balance.