Abstract： Objective： To observe the clinical effect of Shenling Baizhu San Decoction combined with western medicine for diarrhea- predominant irritable bowel syndrome (IBS- D) with spleen deficiency and prevalence of dampness Syndrome. Methods： A total of 120 cases of IBS- D patients with spleen deficiency and prevalence of dampness were selected as the study objects，and divided into two groups according to the random number table method，with 60 cases in each group. The control group was treated with Live Combined Bifidobacterium and Lactobacillus Tablets，and the trial group was additionally treated with Shenling Baizhu San Decoction based on the treatment of the control group. Traditional Chinese medicine (TCM) syndrome scores and levels of T- lymphocyte subsets before and after treatment， and clinical effects were compared between the two groups. Results：The total effective rate was 96.67% in the trial group and 83.33% in the control group，the difference being significant (P＜0.05). After treatment， the TCM syndrome scores including main symptoms and secondary symptoms in the two groups were decreased when compared with those before treatment (P＜0.05)，and the scores of main symptoms and secondary symptoms in the trial group were lower than those in the control group (P＜0.05). After treatment，the levels of T-lymphocyte subsets including CD3+，CD4+，and CD4+/CD8+ in the two groups were increased when compared with those before treatment (P＜0.05)， and the levels of CD8 + were decreased (P＜0.05)；the levels of CD3+，CD4+，and CD4+/CD8+ in the trial group were higher than those in the control group (P＜0.05)，and the level of CD8+ in the trial group was lower than that in the control group (P＜0.05). Conclusion： The therapy of Shenling Baizhu San Decoction combined with Live Combined Bifidobacterium and Lactobacillus Tablets has a significant therapeutic effect on IBS-D patients，which can effectively improve TCM syndrome and immune function of patients.