ZHANG Yuan-su is the inaugurator of Yishui school，who is good at analysising etiological factors and pathogenesis by cold-hot syndrome and deficiency and excess of zang-fu viscera.Also he has form a Theory system of visceral syndrome differentiation.By summarizing the nature and flavour of TCM and theory of interrelationship of generation and restraint，he has carried on the theory of the Yellow Emperor’s Internal Classic，even innovating it.His theory is more helpful to clinical treatment，also is worth to learn.