Objective To investigate the efficiency and safety of endoscopic large balloon dilation following small sphincterotomy (ESBD) for treatment of common bile duct (CBD) stones, and to prospectively compare it with traditional sphincterotomy (ES). Methods Patients with single or multiple calculi in extra-hepatic bile ducts and with the diameter of CBD larger than 13 mm, were randomized into 2 groups to receive maximal sphincterotomy (ES group), or partial sphincterotomy plus sphincteroplasty with 15mm-balloon (ESBD group), respectively, followed by conventional stones removal and/or lithotripsy. The success rate of stone clearance, operation time and related complications were observed. Results A total of 86 patients were enrolled in 2 endoscopy centers, with 2 excluded because of papillary pre-cut in 1 and non-compliance with the protocol in the other, and were randomly divided into groups ES and ESBD, with 42 patients in each. The clinical characteristics, including average diameter of CBD, size and quantity of calculi, and incidences of peri-ampullary diverticulum, of patients in both groups were all similar. Stones clearance with single session in 2 groups were 88% and 93%, respectively (P =0. 531 ). The operation time were (25.76 ± 12. 74) min and (26. 38 ± 12. 86) min ( P = 0. 825 ). The rate of mechanical lithotripsy was 36% and 25%, respectively (P=0. 363). Complications occurred in 5 cases in ES group (3 mild, 2 medium), and 2 mild complications occurred in ESBD group (no statistical difference). No death happened in any group.Conclusion ESBD is an effective method for clearance of extra-hepatic bile duct stones with the similar safety, compared with traditional sphincterotomy. It could be an optimal alternative for those with large stones or difficult sphincterotomy.