Huangdi Neijing, referred to as Neijing for short, is the earliest extant classic work of TCM theory in China, and it is also the first of the four classic works of Chinese traditional medicine (Huangdi Neijing, Treatise on Febrile Diseases, Synopsis of the Golden Chamber and Treatise on Febrile Diseases).

Neijing is an "encyclopedia" with life science as the main body, which conveys the traditional philosophical thoughts and thinking methods, astronomy, calendar, meteorology, phenology, geography, sociology, psychology and even mathematics that people mastered before and after the Han Dynasty to explore the mysteries of life and reveal the essence of life.

Neijing theoretically established the theories of yin and yang, five elements, pulse condition, Tibetan image, meridians, etiology, pathogenesis, symptoms, diagnosis, treatment, health preservation and luck.

Neijing is a master of Chinese ancient medical theoretical documents, which was not written in a short time or by one person. Its main part should be a book compiled in the middle and late Western Han Dynasty, which was recorded in Liu Xin's Qilue in about 26 BC. However, Sima Qian's Historical Records recorded that the same medical books were quoted in the Internal Classic, but the Internal Classic was not seen. It can be seen that the book of Neijing should be written between 99 BC and 26 BC, which lasted more than 60 years.

Neijing is divided into Su Wen and Ling Shu, with a total of 18 volumes and 162 articles. Su Wen focuses on viscera, meridians, etiology, pathogenesis, symptoms, diagnosis, treatment principles and acupuncture.

Lingshu is an inseparable companion of Su Wen, and its contents are basically the same. In addition to discussing the function, etiology and pathogenesis of viscera, it also focuses on meridians and acupoints, acupuncture, acupuncture methods and treatment principles.

Neijing comprehensively summarized the medical achievements before Qin and Han Dynasties, and its completion marked the rise of China medicine from empirical medicine to theoretical medicine.

This paper summarizes the achievements of medicine before the Warring States Period in the aspects of holism, contradiction, meridian science, viscera images, etiology and pathogenesis, health care and preventive medicine, diagnosis and treatment principles, etc., which provided theoretical guidance for the development of China medicine after the Warring States Period, laid a solid foundation and had a far-reaching impact.