Gastric bypass surgery, a surgery to change the structure of the intestine and shut down most of the gastric function, surgically divides the stomach into two parts, the smaller upper part, and the larger lower part, then truncates the small intestine, rearranges the position of the small intestine, changes the pathway of food through the digestive tract, slows down gastric emptying, shortens the small intestine, and reduces absorption. Although the mechanism of gastric bypass surgery for the treatment of diabetes remains to be studied in depth, from the completed surgeries, the following three main effects have been achieved: 1. the upper duodenum and jejunum, which mainly absorb sugar, are left open; 2. the effect of weight loss and reduced food intake; and 3. the effect of hormonal changes in the body. Diabetes occurs due to the stimulation of the mucosal wall cells of the upper part of the distal duodenal jejunum of the stomach by food, which produces insulin resistance cytokines, producing insulin resistance; after surgery, food no longer passes through the above-mentioned area, and the secretion of insulin resistance factors decreases or stops. On the other hand, after surgery, food enters the middle and lower gastrointestinal tract directly, stimulating its mucosal wall cells, and PYY (gastrointestinal kinins) and GLP- 1 (glucagon-Like Peptide-1) cytokines are consistently and significantly elevated, lowering blood glucose, suppressing hyper-appetite, promoting islet cell proliferation, slowing down the rate of islet apoptosis and accelerating the rate of proliferation, reducing insulin resistance, and leading to improvement of islet failure.