Abstract：Objective：To observe the clinical effect of Tongxiening granules combined with mesalazine for irritable bowel syndrome with diarrhea(IBS-D). Methods：A total of 62 cases of IBS-D patients were randomly divided into the control group and the treatment group，31 cases in each group. The control group was treated with mesalazine，and the treatment group was additionally treated with Tongxiening granules based on the treatment of the control group. Before and after treatment， the changes in syndrome scores and levels of immunological indexes including IgG， IgM and IgA in the two groups were observed and compared. The total clinical effect in the two groups was counted. Results：The total effective rate was 83.87% in the treatment group and 54.84% in the control group，the difference being significant(P＜0.05). After treatment，the levels of IgG，IgM and IgA in the two groups were significantly decreased when compared with those before treatment(P＜0.05)， and the above indexes in the treatment group were significantly lower than those in the control group(P＜0.05). After treatment， the syndrome scores including abdominal pain， abdominal distension and diarrhea in the two groups were significantly decreased when compared with those before treatment(P＜0.05)，and the above scores in the treatment group were significantly lower than those in the control group(P＜0.05). Conclusion：The therapy of Tongxiening granules combined with mesalazine for IBS-D has significant curative effect and can significantly regulate immune function of the body，whose curative effect is better than that of western medicine.