Diabetes mellitus is a chronic metabolic disease with a high incidence. Diabetic patients with long-term poor glycemic control are prone to complications such as heart, brain, kidney, nerve and fundus chronic complications, which affect patients’ quality of life and increase medical costs. Therefore, effective prevention of diabetes and implementation of tertiary prevention measures are needed. The purpose of the three levels of diabetes prevention are: 1. primary prevention, for people at high risk of diabetes, early detection of possible diabetes, lifestyle intervention, and delay of diabetes. 2. secondary prevention, for patients with diagnosed diabetes, lifestyle intervention, guidance of rational use of drugs, good control of blood sugar, and prevention of complications. 3. tertiary prevention, for people with diabetes For patients with long duration of diabetes and complications, to slow down the development of complications as much as possible, to reduce the rate of disability and death due to diabetes, and to improve the quality of life of patients.