Objective To systematically evaluate the effectiveness of frequently-used bariatric surgery versus conventional medical therapy for obese patients with type 2 diabetes. Methods Such databases as The Cochrane Library (Issue 12, 2012), PubMed, CNKI, CBM, VIP and WanFang Data were searched to collect the randomized controlled trails (RCTs) about frequently-used bariatric surgery vs. conventional therapy for obese patients with type 2 diabetes. The retrieval time was from inception to May, 2012. Two reviewers independently screened the literature according to the inclusion and exclusion criteria, extracted the data, and evaluated the quality. Then the meta-analysis was performed using RevMan 5.1.2 software. Results A total of three RCTs involving 340 patients were included finally. The results of meta-analysis showed that, compared with conventional medical therapy, bariatric surgery could improve the diabetes remission, decrease both glycated hemoglobin level and patient’s weight. At the same time, the postoperative complications were fairly mild. Conclusion Frequently-used bariatric surgery is superior to conventional medical therapy when treating obese patients with type 2 diabetes, and it deserves to be recommended in clinic. However more studies are required to further confirm this conclusion because of the quality and quantity limitation of the included studies.