Abstract：Objective：To observe the curative effect of Jiedu Guben tang combined with western medicine for ulcerative colitis and its effect on intestinal flora and immune function. Methods：A total of 120 cases of patients with ulcerative colitis were selected and divided into the observation group and the control group according to the random number table method， with 60 cases in each group. The control group was treated with routine western medicine，and the observation group was additionally treated with Jiedu Guben tang based on the treatment of the control group. Both groups were treated for six weeks. The clinical effects in the two groups were observed. Before and after treatment，the changes in Chinese medicine syndrome scores， intestinal flora including escherichia coli， lactobacillus and bifidobacterium as well as indexes of T lymphocyte subsets in serum including CD3 + ， CD4 + and CD4 +/CD8 + in the two groups were compared. Results： After treatment，the Chinese medicine syndrome score was 11.77±2.31 points in the observation group and 16.87±3.05 points in the control group， the difference being significant(P＜0.05). After treatment， the total effective rate of clinical effect was 96.67% in the observation group and 85.00% in the control group，the difference being significant(P＜0.05). After treatment， the numbers of escherichia coli in the two groups were decreased when compared with those before treatment， and the numbers of lactobacillus and bifidobacterium were increased， differences being significant(P＜0.05)； the numbers of lactobacillus and bifidobacterium in the observation group were greater than those in the control group，and the number of escherichia coli was smaller，differences being significant(P＜0.05). After treatment，the levels of CD3 +，CD4 + and CD4 +/ CD8+ in the two groups were increased when compared with those before treatment，differences being significant(P＜0.05)； the levels of the above three items in the observation group were higher than those in the control group，differences being significant(P＜0.05). Conclusion： The therapy of Jiedu Guben tang combined with western medicine for patients with ulcerative colitis can effectively alleviate their symptoms of abdominal pain and diarrhea，improve intestinal flora and relieve inflammation.