To observe the clinical curative effect of self-made antidiarrheal decoction in the treatment of pediatric protracted diarrhea and some of its regulatory mechanism. Methods: One hundred cases of pediatric protracted diarrhea treated in our hospital during March 2010 to March 2013 were included in the study. Fifty cases in the control group accepted medical conventional treatment， and the other 50 cases in the observation group received self-made antidiarrheal decoction apart from the same treatment of the control group. The treatment course of both groups was 10 days. The symptoms changes of children in the two groups after treatment was observed. Simultaneously flow cytometry was used to test peripheral blood expression level of Th17 cells， and ELISA was used to detect the protein expression level of IL-6， IL-17， IL-23 in the serum of patients. Results: 1) Temperature recovery time， vomiting stop time of the two groups were with no statistical differences (P>0.05)， but the diarrhea stop time of the observation group was shorter than that of the control group (P<0.05). 2) after treatment， serum IL-6， IL-17， IL-23 levels in children in the two groups with lower than those before treatment (P<0.05)， and after one period of treatment， IL-17， IL-6， IL-23 levels of the observation group declined significantly than those of the control group (P<0.01). 3) after the 3 months follow-up， childrens weight gain of the observation group was obviously more than that of the control group (P<0.05). Conclusion: Children with protracted diarrhea have increased expression of Thl7 cells and hyperfunction， and self-made antidiarrheal decoction can obviously down-regulate frequency and function of Thl7 cells expression which may be one of the mechanisms of self-made antidiarrheal decoction improving protracted diarrhea in the aspects of the bodys immune ability.