By combing the original text of Treatise on Febrile and Miscellaneous Disease, referring to the theories of different schools, and combining with the theory of essence qi in Chinese classical philosophy and traditional Chinese medicine, it is considered that Shenqi Wan (pill for invigorating kidney qi) promotes the vaporization function of the kidney mainly by stimulating kidney essence transforming into kidney qi, that is, minor fire generating kidney qi. The medicine is mainly used to treat the disease with retention of fluid and dampness caused by failure of essence transforming into qi and dysfunction of qi transformation.