ABSTRACT
"If slight diarrhoea, replacing Ephedra with Daphninae"under the article 40 of Treatise on Febrile Diseasesis is controversial. There are two different opions in all physicians, one explaination it is in line with Zhang Zhongjing but without the evidence about"replacing Ephedra with Daphninae"; the other is that Daphninae is too strong to apply in diarrhoea. According to the analysis on Treatise on Febrile and Miscellaneous Diseases, the slight diarrhoea is the phenomenon of Vital qi exorcism. The reason why replacing Ephedra owing to exogenous evil disappearance, the construction of Daphninae Pinellia ternate and Paeony is to expell the water on the leaving way. And we draw a conclusion that the function of Paeony in Xiaoqinglong decoction is inclined to be expelling Water Qi.