Abstract: Bariatric surgery is an effective treatment for obesity and the related metabolic diseases. At present, although the jejunoileal bypass is widely used in various types of bariatric surgery, the effect of reconstructed anatomy after the jejunoileal bypass on normal physiological function of obese patients has not been clarified. This leaves some controversy about the recommended limb lengths in jejunoileal bypass. At the same time, there is no consensus on the optimal biliary limb length and alimentary limb length in the standard gastric bypass. Lack of accurate measurement of common limb length and total small bowel length inevitably results in unsatisfactory percentage of excess body weight loss caused by short limb length, or malabsorption and malnutrition caused by long limb length. The authors discussed the effects of different length of biliary limb, alimentary limb and common limb on weight loss, and introduced the preliminary application and prospects of the jejunoileal bypass including measurement of total small bowel length in bariatric surgery.