Huangdi Neijing is the earliest and most complete medical classic document in China. This paper summarizes the clinical medical practice experience before Qin and Han dynasties, and comprehensively describes the ancient medical thoughts, knowledge and methods such as yin and yang, five elements, five movements and six qi, zang-fu organs and meridians, diagnosis and treatment, acupuncture prescriptions and drugs. Its appearance marks the initial formation of the theoretical system of ancient Chinese medicine and lays the foundation of Chinese medicine theory. Huangdi Neijing has a total of 18 volumes, of which Suwen and Zhen Jing (renamed Lingshu after the Tang Dynasty) have 9 volumes each. The medical thought, clinical knowledge and technology recorded in the book reflect the ancient people in China's understanding of human life activities and diseases, and their wisdom in overcoming diseases. Huangdi Neijing correctly records and discusses the position, shape and physiological function of the internal organs of human body, and points out that "the heart governs the blood vessels of the body", blood can be divided into turbid and turbid, and it is "popular and infinite" through the function of "the lung facing a hundred pulses", and the beating of the heart can be measured by "the pulse in the mouth" and "the pulse in the virtual interior". This is the earliest theory of blood circulation in the world, which correctly reveals the relationship between heart and blood circulation. It is nearly 2000 years earlier than the theory of small blood circulation known to Arabs in 13 century and the theory of blood circulation put forward by western European doctors in 16 and 17 century. Huangdi Neijing uses simple dialectical thought of Yin-Yang and Five Elements to explain the human tissue structure and its movement law, and establishes a unique theory of Tibetan images. In other words, the human body is centered on the five internal organs, and contacts the whole body through the meridian system during the movement of ascending and descending essence (including blood and body fluid). Each of the five zang-organs has its own system, which participates in the physiological activities of the human body in different ways. The zang-fu organs are interrelated and mutually restricted, forming an organic whole of life and running harmoniously. The theory of Tibetan image expounded in Huangdi Neijing has always had a great influence on the understanding of human physiological functions by later doctors, and it is the theoretical cornerstone of TCM physiology. Huangdi Neijing summarizes and expounds the internal mechanism and internal and external causes of diseases, and holds that the mechanism of diseases mainly depends on the strength of healthy qi and external pathogenic factors. If the human body is full of healthy qi, even if there are diseases outside, it is not easy to get sick; On the contrary, if healthy qi is weak, pathogenic factors will take advantage of it and cause diseases. In other words, the internal cause is main, but the external cause can not be ignored. Huangdi Neijing further supplements and develops on the basis of summarizing the experience of previous diagnosis methods, and clearly puts forward four diagnoses of "looking, smelling, asking and feeling" in traditional Chinese medicine. Up to now, four diagnoses are still the basic methods of clinical diagnosis of diseases in traditional Chinese medicine. There is a considerable discussion on acupuncture in Huangdi Neijing. This book discusses the application scope of acupuncture in treating diseases, makes theoretical research on acupuncture treatment and acupuncture anesthesia, and introduces the application of acupuncture technology in detail, which provides valuable information for the research and development of acupuncture. In addition, Huangdi Neijing also recorded the treatment prescription, health care and so on. The extensive description and profound theory in the book are like "Ozawa in the deep mountains, born with dragons and snakes", which is a great medical treasure house.