To observe the clinical effect and the cellular immune function of Jiexie decoction in treating acute diarrhea and its mechanism.Methods:A total of 88 cases with acute diarrhea in the emergency department of our hospital admitted from January 2016 to December 2016 were randomly divided into observation group and control group, with 44 cases in each group.Forty healthy cases in the department of physical examination were taken as control group.The control group was treated with conventional therapy, electrolyte disturbance and anti-infection treatment.On the basis of the control group, the observation group was given modified decoction for 7 days.The symptoms of both groups were evaluated and recorded, and the pathogen was identified.The levels of Th1 and Th2 were detected by flow cytometry.Results:1) In 88 cases of acute diarrhea, the strain of Proteus was the highest, especially Proteus mirabilis was the highest among the 27 strains.2) After treatment, the total effective rate of the observation group (97.73%) was significantly higher than that of the control group (90.90%), but there was no significant difference between the two groups (P>0.05).3) After treatment, the stool frequency of the observation group was significantly lower than that of the control group (P<0.05), but there was no significant difference compared with the healthy control group (P>0.05).After treatment, the abdominal pain score and diarrhea score of the observation group were lower than those of the control group (P<0.05).4) The proportion of Th1/Th2 patients in the observation group was lower than the control group, but it increased after intervention for a period of 7 days.Although compared with the healthy control group is still low, it improved significantly, and the difference was statistically significant (P<0.05).Conclusion:Jiexie Decoction can effectively reduce the frequency of defecation in patients with acute diarrhea, reduce abdominal pain score and diarrhea score, and its mechanism might be related to cellular immune function improvement and Th1/Th2 ratio enhancement.