Obesity and type 2 diabetes are common chronic diseases which severely threatens human's health and lives.In addition to behavioural and medical approaches,the bariatric surgery is increasingly being valued by medical workers.There are many kinds of surgical method of the bariatric surgery,but by far the most popular ones are Laparoscopic sleeve gastrectomy and Laparoscopic sleeve gastrectomy.The mechanism of the surgery may related to gastrointestinal hormones and fat metabolism,but no final conclusion has yet been reached on this matter.This paper is a literature review on the effect and mechanism of bariatric surgery.