With the modern medical science and education becoming more and more advanced, the relevant treatment mechanisms are being deciphered one by one to treat the age-old problem of diabetes. It is believed that in the near future, even if diabetes becomes a common disease, it will be as easy to treat as a cold. But back to reality, the only treatment for diabetes that can be done without the need for lifelong medication to control blood sugar is diabetes surgery. The “gold standard” in bariatric surgery, gastric bypass, has long been the appropriate treatment for obese patients with type 2 diabetes. The mechanism of this surgery for diabetes treatment is not only to restore glucose metabolism by improving insulin resistance through weight loss, but also to change the intestinal flora to directly lower blood sugar. Then, the relationship between intestinal flora and diabetes is also worthy of deeper investigation. The human gastrointestinal tract is home to a variety of microorganisms called the intestinal flora. Human genetic predisposition, infant and child feeding patterns, and dietary habits are all factors that shape the intestinal flora. A growing body of research today suggests that intestinal flora is strongly associated with obesity and type 2 diabetes. Gut flora can influence the development of metabolic syndrome and type 2 diabetes through host energy metabolism, immune system and inflammatory response. The specific manifestations of this are: intestinal flora can influence the absorption of sugars and energy and promote the synthesis and storage of fats in the body. The interaction of intestinal flora with a high-fat diet leads to inflammation and induces insulin resistance. Gut flora is involved in the regulation of fat storage in the host as an important environmental factor; therefore, dysbiosis of the gut bacteria may be an important factor in promoting the development of obesity. Various links suggest that altering the intestinal flora plays an important role in the treatment of diabetes, and gastric bypass surgery effectively controls human blood glucose by simultaneously modifying the intestinal flora in the process of reconstructing the digestive tract. The treatment of diabetes by gastric bypass surgery is a systemic project, not a unilateral treatment mechanism, but a multifaceted treatment from a variety of causes of diabetes, so that patients can generally get good improvement after surgery.