Compendium of Materia Medica puts forward the method of health preservation: four natures and five flavors, and medicine and food are homologous. The so-called "four natures and five flavors" means that food supplements are divided into four qi and five flavors, and the four seasons should be avoided, which fully embodies the idea of "preventing diseases" in traditional Chinese medicine. According to the theory of traditional Chinese medicine, food and medicine are divided into five flavors: sour, bitter, sweet, pungent, salty, cold, hot, warm and cool. According to the different physical characteristics of the human body and the yin-yang cold-heat bias of diseases, those who are hot are cold, and those who are cold are hot. In fact, they are diarrhea, and deficiency is tonic, so as to better regulate the five internal organs, strengthen the body resistance and eliminate evil. This theory, together with the theory of homology of medicine and food, may be the theory of four natures and five flavors. In addition, the theory of homology of medicine and food seems to have been involved as early as Huangdi Neijing, and it was not put forward for the first time in Compendium of Materia Medica, but it was more detailed and richer in content.