Diabetes mellitus (T2DM) is the most common complication of obesity patients. According to previous literature reports, weight loss and metabolic surgery are powerful means to treat obesity complicated with T2DM. Roux-en-Y gastric bypass (RYGB) is the standard operation recommended by the international society. One-anastomosis gastric bypass (OAGB) was recommended by IFSO（the International Federation for the Surgery of OBESITY AND METABOLIC DISORDERS ） in 2018. In this study, two kinds of metabolic surgery will be compared. At present, focusing on the above two operations, only two effective randomized controlled clinical studies have been carried out, among which one single-center clinical study has been followed up for 2 years, and the primary end point is weight loss; Another multicenter study, with a 2-year follow-up, showed that the primary end point was weight loss, and the secondary index was the effectiveness of two surgical methods in the treatment of T2DM.There is still a lack of evidence-based evidence for the effectiveness and safety of the two surgical methods in the treatment of T2DM. This study will make high-level evidence about the advantages and disadvantages of OAGB and RYGB in the treatment of T2DM. In this study, a number of centers with rich experience and clinical research experience in weight loss and metabolic surgery in Asia will be combined to complete the enrollment of 248 patients. Those who meet the standards will be randomly divided into two kinds of operations, and they will be followed up for 5 years on schedule. The rate of lost follow-up is controlled within 20%, and the data integrity is controlled within 95%. Taking the blood glucose remission rate of type 2 diabetes as the main observation index, the prospective verification shows that OAGB is clinically effective in treating obesity with type 2 diabetes compared with RYGB.