To analyze the mechanism of “promoting urination to treat diarrhea” and discuss the functions of kidney and small intestine on fluid metabolism.Methods:A total of thirty rabbits were randomly divided into normal control group(10), model control group(10), and Wulingsan group(10). The normal control group was given 10 mL normal saline, which was given intragastrically twice. The model control group was given Wulingsan and 8% Folium Sennae powder at the same time, once, intragastrically. Incubation of diarrhea was (1.22±0.26)h. The observation group was given Folium Sennae powder firstly and after 1.5 h, Wulingsan was given. Then observe serum BUN and Scr, PSP, absorbing capability of small intestines, and the tension and contraction force of jejunum.Results:Compared with model control group, all levels are better in the observation group(P<0.05) except for the absorbing capability of small intestine(P>0.05).Conclusion:The mechanism of “promoting urination to treat diarrhea” originates from the the function of kidney and the movement of small intestine, and it has nothing to do with the absorbing capability of small intestine. Therefore, the function of fluid regulation of small intestine should be discussed from the angle of the correlation between kidney and small intestine.