Objective: To observe the effect of Liancao-Xieli Capsule on STAT signal pathway and T cell differentiation in mouse model of ulcerative colitis; Methods: Forty BALB/c mice were randomly divided into the control group, model group, mesalazine group and Liancao-Xieli capsule group. Except the control group, the other three groups were treated with 3％ dextran sodium sulfate free drinking water to construct the model of ulcerative colitis. During the modeling period, each group was given corresponding drugs for intervention, while the control group and the model group were given the same volume of distilled water by gavage as the control. After treatment, HE staining was used to observe the pathological changes of colon tissue, flow cytometry was used to detect the proportion of Th17 and Treg cells in spleen and mesenteric lymph nodes, and ELISA was used to detect TGF-β, IL-6 and IL-17A in colon tissue. Western blot was used to detect the expression levels of related proteins in STAT3/ROR-γt and STAT5/Foxp3 signaling pathways. Results: Compared with the model group, the body weight, colon length and the content of TGF-β in the colon tissue of the mice in the Liancao-Xieli capsule group increased significantly after the experiment, while the DAI score, colon histopathology score, and the contents of IL-6 and IL-17A in the colon tissue were significantly reduced, and the difference was statistically significant (P<0.01). At the same time, Liancao-Xieli capsule can reduce the ratio of Th17 cells and the ratio of Th17/Treg in the spleen and mesenteric lymph node tissues of UC mice, and increase the ratio of Treg cells, and the difference is statistically significant when compared with the model group (P<0.01). In addition, compared with the model group, the expression levels of p-STAT3 and ROR-γt protein in the colon tissue of the Liancao-Xieli capsule group were significantly reduced, and the expression levels of p-STAT5 and Foxp3 protein were significantly increased after treatment, and the differences are statistically significant (P0.05); Conclusion: Liancao-Xieli Capsule can regulate the immune balance of Treg/Th17 and improve the intestinal inflammation of UC. Its mechanism of action is mainly through inhibiting STAT3/ROR-γt and promoting the activation of STAT5/Foxp3 signaling pathway.