Canon of Medicine（Nei Jing）is the earliest classic of the existing medical literature of China. The book is divided into Plain Questions（Su Wen）and Miraculous Pivot（Ling Shu）,collecting 162 papers. It elaborates systematically the structure, physiology and pathology of the human body, the diagnosis and treatment of diseases, health maintenance and other problems, forming the theoretical basis of TCM. Its main contents include visceral manifestations, meridians and collaterals, pathogenic factors, pathogenesis, diagnostic methods, treating principles, acupuncture and moxibustion, and decoctions, etc. It elaborates medical theories, and at the same time, discusses a series of major issues in the field of philosophy, such as the concept of Qi, the relationship between human beings and nature, the relationship between body constituent and spirit in depth. Many contents in Canon of Medicine are beyond the world level at that time, for example, in the aspect of morphology, its records on the length of human bones and blood vessels, the size and capacity of internal organs are true, for instance, the ratio of the oesophagus to the intestine is 1:35, and in modern anatomy it is 1:37, which are very close; in the aspect of physiology, it has presented the idea that"blood circulation in the vessels is controlled by heart" and recognized that blood circulates in the blood vessels. The great theoretical contribution of Canon of Medicine（Nei Jing）lies in summarizing the medical experience and academic theory of the Spring and Autumn period, the Warring States period and Qin and Han Dynasties, establishing the unique theoretical of traditional Chinese medicine and becoming the basis for the development of traditional Chinese medicine.
The classic of Difficult Issues（NanJing）contains a total of 81 questions and answers, so it is also known as"81difficulties". It elaborates the body structure, physiology, pathogenic factors, pathogenesis, diagnosis, creating principles and methods, etc, and especially its contents about pulse diagnosis and acupuncture treatment are more detailed than Canon of Medicine（Nei Jing）. It is comparable with Canon of Medicine at that time, and also has important guiding significance for the clinical practice of later ages.
In the last years of the Eastern Han dynasty, Zhang Zhongjing, a famous physician, further summarized the previous medical achievements and combined them with his own clinical experience, and finally wrote the clinical monograph Treatise on Cold Damage and Miscellaneous（Shang Han Za BingLun）on the basis of Canon of Medicine（Nei Jing）and Classic of Difficult Issues（Nan Jing）. It advocates diagnosing and treating exogenous diseases and endogenous diseases on the basis of six-meridian syndrome differentiation and visceral syndrome differentiation, and thus it establishes the system of syndrome differentiation and treatment of traditional Chinese clinical medicine and the applying principles of syndrome differentiation, treating methods, prescriptions and herbs, which lays the foundation for the later development of clinical medicine. It was compiled into Treatise on Cold Damage Diseases（Shang Han Lun）and Synopsis of Prescriptions of the Golden Chamber（Jin Gui Yao Lue）by Wang Shuhe, a TCM doctor of Jin dynasty.
Shennong's Classic of Materia Medica（Shen Nong Ben Cao Jing）was written in the Han dynasty with Shennong's name. It is the first classic on material media in China, which records 365 kinds of drugs and summarizes systematically the pharmaceutical knowledge of the Han dynasty and before the Han dynasty. It divides the levels of drugs into upper, middle and lower based on health maintenance, treatment and toxicity, and divides the properties of drugs into cold, cool, warm and hot and the flavours of drugs into sour, bitter, sweet, acrid and salty according to the efficacy of the drugs. It lays the foundation for the formation and development of the theoretical system of Chinese medicine of the later ages.