“Clear” state is the fundamental guarantee for the health, and “non clear” state of the body can lead to the tumor. The importance of “clear” state in the prevention and treatment of tumor is explained from “clear orifices”, “clear qi” and “clear spirit” and so on. It is considered that the “clear” state of the body is the guarantee of realizing correspondence between nature and human and maintaining harmony between body and spirit. It is the foundation of the orderly store and discharge of zang-fu organs and the smooth flow of qi,blood and meridians. It is also the key to dispelling pathogens and attacking toxin out of the body and preventing the formation of cancer.