Strict control of diet is a prerequisite for the treatment of diabetes and is the most important part of the diabetes treatment process. I believe that many clinicians in medical practice will find that some diabetic patients have poor dietary control, so that the drugs do not work as effectively as they should, which eventually leads to unsatisfactory blood sugar control and even complications. Many patients are also confused about how to control their blood sugar even though they have already taken so many kinds of medications. Diet therapy is the basic treatment for diabetes and is the prerequisite for all treatments, and is applicable to all types of diabetes patients. In light cases, diet therapy is the main treatment to receive good results, while in medium and heavy cases, exercise therapy and drug therapy must be applied reasonably on the basis of diet therapy. Only if the diet is well controlled, oral hypoglycemic drugs or insulin can play a good role. Otherwise, it is wrong and dangerous to rely on the so-called new drugs and good drugs and ignore the diet, thinking that taking more glucose-lowering drugs can make you eat more, trying to rely on glucose-lowering drugs to offset the excessive intake of energy and sugar, similar to the concept of “whipping a sick horse”. Diet therapy calculates the total daily calorie requirement by the patient’s height, weight, age and condition. The total calorie requirement can be relaxed for lean patients to ensure the total calories. Obese patients must strictly control the total calories and lose weight with a low-calorie fat diet. With the total intake then different nutrient ratios are formulated according to the condition of different patients, and finally a reasonable intake for each meal is derived. While diabetic patients are on diet therapy, the program can be adjusted at any time according to their condition. Diet therapy should be scientific and reasonable, not too much and not too little. In other words, it should not be subjective and arbitrary, eating this and that too; nor should it be too restrictive, not eating this and that too. Under the premise of controlling the total calories, the diet should be arranged scientifically and reasonably to achieve the purpose of both meeting the minimum needs of the body and controlling the total calories. Through a period of diet therapy, the following objectives can be achieved: 1. Reduce the burden on the pancreas, help patients achieve and maintain better metabolic control, bring blood sugar, urine sugar and blood lipids to or near normal values, and prevent or delay the occurrence and development of cardiovascular and other complications. 2.Maintain health, so that adults can engage in various normal activities and children can grow and develop normally. 3.Maintain or reach a healthy weight. Reducing energy intake in obese people can improve the patient’s sensitivity to insulin, and in lean people can make weight gain to enhance resistance to various infectious diseases. Finally, it is important to note that only long-term adherence to dietary therapy can achieve the goal of controlling diabetes and its complications. And depending on the different stages of the body with different diseases, the diet therapy should be adjusted appropriately to ensure the different needs of the organism.