Primary prevention, secondary prevention and tertiary prevention are the three levels of disease prevention, which refer to the adoption of corresponding public health preventive measures in the target population according to the three levels for the different stages of disease. The first level of prevention, also known as etiologic prevention, refers to the adoption of appropriate measures against the causes or risk factors of diseases before they occur, in order to prevent or delay their occurrence. The second level of prevention is also known as “three early” prevention, i.e. early detection, early diagnosis and early treatment. It refers to the early detection and diagnosis of diseases at the early stage of the disease through screening tests and regular medical check-ups, etc., and the timely provision of appropriate treatment to achieve the purpose of curing or delaying the development of the disease process. The third level of prevention, also known as clinical prevention or disease management, refers to the reduction of the burden and harm brought by disease to individuals, families and society through appropriate treatment after the signs and symptoms of the disease have clearly manifested. The theoretical system of tertiary prevention of disease is centered on disease prevention, which plays an important role in the field of modern preventive medicine and is of great significance to the maintenance of the health of all people.