Abstract: OBJECTIVE To investigate the efficacy of Baitouweng decoction enema in the treatment of ulcerative colitis patients and its effect on T cell subsets. METHODS 124 patients with ulcerative colitis admitted to our hospital from January 2014 to March 2018 were randomly divided into control group and observation group. Both groups were given mesalazine and the observation group was additionally treated with Baitouweng decoction enema. The effectiveness rate of treatment， colonscopy score， length of stay， UC activity， T cell subsets change and the incidence of adverse reactions were compared between the two groups. RESULTS After 30 days of treatment， the effectiveness rate of treatment in observation group(93.5%) was significantly higher than that in control group (72.6%)， P <0.05. The length of stay in observation group was significantly lower than that in control group ( P <0.05). The DAI score in observation group was significantly lower than that in control group， P <0.05; The CD3⁺ and CD8⁺ in peripheral blood of both groups showed a downward trend while both CD4⁺ and CD4⁺/CD8⁺ showed an upward trend， and the change range of the observation group was significantly larger than that of the control group， P <0.05. The incidence of adverse reactions in observation group was 9.7% and the control group counterpart was 8.1%. The difference was not significant( P >0.05). CONCLUSION Baitouweng decoction enema can effectively improve the efficacy of UC， reduce the UC activity index and the length of stay， improve the immune function of patients， which is worthy of further promotion and application in clinical practice.