Objective: To explore the mechanism of Pi (Spleen)-deficiency-induced functional diarrhea (FD)model rats treated by Shenling Baizhu Powder(参苓白术散,SBP).Methods: Thirty male Sprague-Dawley rats were randomly divided into 5 groups including control,model,low-,medium-,and high-dose SBP groups (SBPLDG,SBPMDG,SBPHDG),6 rats in each group,respectively.Pi-deficiency-induced FD rats model was developed through Radix et Rhizoma Rhei gavage for 7 days.After modeling,the rats were treated with 3 doses of SBP[0.93,1.86,and 3.72 g/(kg·d)],and the rats in the control and model groups were given pure water for 7 days.The diarrhea index was calculated.On the 7th and 14th days,the traveled distance of rat was measured by the open field test.Serum D-xylose content was determined by the phloroglucinol method and interleukin (IL)-10 and IL-17 levels were measured using an enzyme-linked immunosorbent assay kit.The content of Treg cells was determined by flow cytometry.Results: Compared with the control group,the diarrhea index and IL-17 level in the model group were significantly higher and the total exercise distance and D-xylose content significantly decreased (P＜0.05).The expression of IL-10 in the SBPHDG group was significantly up-regulated,and serum D-xylose level and Treg cells increased significantly compared with the model group (P＜0.05).Conclusion: High-dose SBP exhibited ameliorating effects against Pi-deficiency induced FD,which might be attributed to its modulations on intestinal absorption function as well as adaptive immunity in mesenteric lymph nodes of rat.