The unique feature of gastric bypass surgery in treating diabetes is that it changes the physiological flow of food, which is accomplished through the steps of gastric blockage, gastrointestinal anastomosis, and enteroenteric anastomosis, thus resolving the diabetes at its root. Surgery stimulates the secretion of many related functional cells in the distal part of the intestines, which increases insulin sensitivity and reduces insulin resistance; surgery also changes the secretion and expression of many gastrointestinal hormones, which promotes the proliferation of pancreatic β-cells and improves pancreatic islet function, and thus diabetes mellitus is well relieved; not only that, surgery can also correct the accumulation of fat due to mono-pure obesity, and thus is the best choice for the treatment of obese patients with type 2 diabetes mellitus. It is also the best option for obese type 2 diabetics. The treatment of diabetes is a systematic project, in order to ensure the therapeutic effect, it needs to be guaranteed by the collaboration of multiple disciplines such as endocrinology, surgery and medical rehabilitation, including strict preoperative screening of indications, individualized design of surgical programs and parameters, correct perioperative symptomatic treatment of various conditions, standardized health guidance, and perfect follow-up, etc. It is understood that gastric bypass surgery can be used to treat diabetes mellitus, but it is also the best choice for obese patients with type 2 diabetes mellitus. It is understood that gastric bypass surgery in the treatment of diabetes mellitus has four major advantages, which has become the choice of many patients with type 2 diabetes mellitus: 1, patients get rid of lifelong medication, do not need to control diet. There are two main causes of diabetes: one is insulin resistance. The second is islet failure. After gastric bypass surgery, the phenomenon of insulin resistance is eliminated, pancreatic islet function is restored, and diabetes is cured. 2.Diabetes complications get recovery. Internal medicine to take drugs can not reverse the complications that have occurred in patients wait until the relief, and after gastric bypass surgery, the patient will not appear in the hands and feet numbness, retinopathy, diabetic foot, urinary protein abnormalities, hypertension and other diabetes complications. 3, to avoid the occurrence of diabetes-induced disability, death. Diabetes that develops to a serious degree can pose a serious threat to a person’s life. After gastric bypass surgery, blood sugar is normalized and complications no longer occur, reducing the harm of diabetes. 4. Blood sugar control and weight loss for obese patients. Gastric bypass surgery can bring some unexpected results to patients, obese patients achieve satisfactory weight loss after surgery.