This paper analyzes experience of treating epidemic febrile disease “Fluid and sweat in saving yin”. “Save yin not in blood but fluid and sweat” is Ye Tianshi’s experience in treating epidemic febrile disease. We argued that this should be explained like this:it is easy to sweat in epidemic febrile disease, so it is important to save yin according to the balance of positive and evil. On the theory of epidemic febrile disease, to save yin is to enrich fluid to sweating.