Type 2 diabetes mellitus (T2DM) accounts for more than 90% of all cases of diabetes mellitus. Worldwide, more than 150 million people suffer from type 2 diabetes. Many factors are involved in its etiology and pathogenesis, and research has found that about 75%-80% of type 2 diabetes is related to obesity. The prevalence of type 2 diabetes is five times higher in obese people than in non-obese people, and even mild obesity can cause type 2 diabetes. The current treatment methods, including diet control, physical exercise, changing bad habits, oral hypoglycemic drugs and insulin use, can rarely make the patient’s blood sugar completely return to normal and cannot prevent the emergence and further aggravation of various diabetic complications. It is such a headache for internal medicine doctors, with the intervention of surgery, ushered in a major breakthrough bariatric surgeons through the clinical observation of obesity surgery found that bariatric surgery can not only make morbidly obese patients to obtain significant and lasting weight loss, but also improve or solve their co-morbid diseases, especially type 2 diabetes. Bariatric surgery has been shown to bring weight loss to obese patients while curing the diabetes that accompanies these patients. These procedures include adjustable gastric banding, sleeve gastrectomy, gastric bypass surgery, and biliopancreatic diversion. Domestic bariatric surgery is dominated by gastric banding, and a large sample of cases reported that about 50% of patients were cured after gastric banding, and the rest improved, with remission of diabetes in parallel with weight loss. Gastric banding is based on the principle of treatment by diet restriction and surgical weight loss. Gastric bypass and biliopancreatic bypass surgery can cure type 2 diabetes, with cure rates ranging from 84% to 100%, depending on the center. 84% of the 240 obese patients with combined diabetes who underwent gastric bypass were cured by Schauer et al. They also found that the common characteristics of patients who only improved but did not cure their disease were a long history of diabetes or old age, and these patients might have islet insufficiency or failure, advanced type 2 diabetes or converted to type 1 diabetes, so it is believed that the functional reserve of the pancreatic cells is one of the factors that determine the outcome of surgery, and it is recommended that early intervention should be made in the surgical treatment of type 2 diabetes. Pories et al. conducted a controlled study of patients who underwent surgery and those who did not, and found that the annual morbidity and mortality rate was much lower in the surgical group than in the conservative treatment group. Gastric bypass and biliopancreatic bypass surgery are collectively referred to as gastrointestinal bypass surgery, and their common feature is that the duodenum and proximal jejunum are left unused as bypasses. Patients usually return to normal blood glucose within one month after gastrointestinal bypass surgery, and remission of diabetes does not coincide with weight loss. The number and type of medications originally needed to control blood glucose are significantly reduced or even discontinued. Most complications of diabetes, depending on their severity, can also be cured. Adjustable gastric banding with the digestive tract intact can also achieve comparable weight loss to gastrointestinal bypass surgery, but the cure rate is much lower than for gastric bypass and biliopancreatic bypass, and most of these cured patients are also in the early stages of diabetes. In contrast, blood glucose returned to normal about 2-3 weeks after gastrointestinal bypass surgery when there was no significant weight loss, which indicates that the improvement of blood glucose after gastrointestinal bypass surgery is not caused by weight loss and dietary restriction alone. Domestic and foreign scholars have analyzed that firstly, significant weight loss after bariatric surgery will lead to the alleviation of insulin resistance and different degrees of improvement of β-cell function, and more importantly, the mechanism is that gastrointestinal bypass surgery also improves glucose metabolism, increases insulin-sensitive phenotype and improves pancreatic β-cell function through changes of gastrointestinal hormones. Rubino et al. showed that obese patients with combined type 2 diabetes already had various endocrine hormone changes 3 weeks after gastric bypass (before there was a significant change in BMI). It is believed that the cure of diabetes after gastric bypass is closely related to the hormonal changes in the intestinal-islet axis. There is sufficient animal and clinical evidence that gastrointestinal bypass surgery, such as gastric bypass and biliopancreatic bypass surgery, rapidly cures type 2 diabetes through the action of various entero-insulinotropic hormones (including CKK, GIP, GLP-1 and Ghrelin) and stimulation of pancreatic islet β-cell function. Glucagon-like peptide-1 (GLP-1) is secreted by L cells distributed in the hindgut (including the distal ileum and colon) and is currently considered to be one of the most important enteric insulinotropic hormones. The rapid arrival of inadequately digested and absorbed food in the distal ileum stimulates GLP-1 secretion by L cells in this region, thereby stimulating and improving pancreatic β-cell function and increasing insulin receptor sensitivity, which is the so-called “hindgut hypothesis”. Second, much evidence suggests that the exclusion of the duodenum and proximal jejunum (collectively referred to as the “foregut”) from the islet axis also plays an important role. Feeding through the duodenum and proximal jejunum in patients with type 2 diabetes may cause some of the abnormal gastrointestinal physiological responses that lead to insulin resistance and diabetes. After the duodenum and jejunum are excluded from the intestinal islet axis, these abnormal gastrointestinal physiological responses are withdrawn. Thus gastrointestinal bypass surgery allows for primary, potent, independent control of diabetes, not secondary to the treatment of obesity. This being the case, then, such surgery should also be effective in slightly obese or nonobese diabetic patients, and current animal studies and clinical studies confirm the effectiveness of this type of surgery in nonmorbidly obese diabetic patients, and over 60% of type 2 diabetic patients have a BMI of 29 or less, who are not severely obese. Although research on surgical treatment of type 2 diabetes is just beginning, a large number of clinical and animal studies have been conducted both at home and abroad, and the efficacy obtained is unmatched by medical treatment. For patients who choose this type of surgery to treat type 2 diabetes, we believe that gastric bypass surgery is more suitable because of its lower risk, morbidity and mortality rate and complication rate compared to biliopancreatic diversion surgery. Moreover, laparoscopic surgery can achieve the same efficacy and less trauma, reduce surgical complications, reduce postoperative pain, shorten hospital stay, resume normal activities early, and have a more aesthetically pleasing abdomen, so we recommend laparoscopic gastric bypass surgery as the best surgical procedure for the treatment of type 2 diabetes. We believe that as the basic and clinical work continues, more and more patients will choose surgery to treat type 2 diabetes. Surgery will open a new chapter in the treatment of diabetes mellitus.