Need. Huangdi Neijing is an encyclopedia of China ancient working people's understanding of the laws of life in heaven and earth. Focusing on expounding the laws of life and medical treatment, this paper comprehensively and systematically summarizes the laws of Yin and Yang about the operation of celestial bodies (cosmology) and the laws of five elements about the generation of everything on earth (biological evolution), and applies the laws of Yin and Yang to the human body (deduction) to understand various phenomena and laws of human body structure and function, pathology and etiology.