Objective: To evaluate the efficacy of reinforcement on duodenal stump using single purse-string suture during laparoscopic radical gastrectomy for gastric cancer in preventing duodenal stump leakage. Methods: A descriptive cohort study was conducted to retrospectively collect clinical data of 211 patients with gastric adenocarcinoma who underwent laparoscopic radical gastrectomy with Roux-en-Y or Billroth Ⅱ reconstruction and reinforcement on duodenal stump using laparoscopic single purse-string suture in Zhongshan Hospital of Fudan University between January 2013 and December 2016. Of 211 patients, 136 were male and 75 were female with mean age of (57.5±11.1)(24 to 87) years. Tumors locating at gastric upper 1/3, middle 1/3 and low 1/3 were found in 62, 68 and 81 patients respectively. Eighty-three cases underwent total gastrectomy, 128 underwent distal subtotal gastrectomy, 107 underwent Roux-en-Y reconstruction and 104 underwent Billroth II reconstruction. The procedure of reinforcement on duodenal stump using single purse-string suture during laparoscopic radical gastrectomy was as follows: (1) after cutting the duodenal stump to about 2.0 cm in length, use a 3-0 single-strand absorbable suture to make a muscle layer purse at a distance of 1.0 to 1.5 cm from the duodenal stump; (2) use the purse line to make a slipknot; (3) push the duodenum stump into the purse with a needle holder or grasper; (4) tighten the knot of the purse string, and then make 4 to 5 knots for reinforcement. Postoperative complications were defined and graded according to the Clavien-Dindo grading criteria, and the incidence of early complications was recorded. Clinicopathologic features and postoperative outcomes were analyzed. Results: All patients completed operations successfully. The mean time of laparoscopic single purse-string suture was (5.1±1.6) (3.6 to 10.2) minutes. Postoperative early complication occurred in 31 cases (14.7%), of whom 27 cases developed surgery-related complications (12.8%), including 7 cases (3.3%) of peritoneal infection, 6 (2.8%) of pancreatic leakage, 4 (1.9%) of wound infection, 4 (1.9%) of gastroplegia, 2 (0.9%) of peritoneal hemorrhage, 2 (0.9%) of intestinal obstruction, 2 (0.9%) of lymphatic leakage, and no duodenal stump leakage; while 4 cases (1.9%) developed internal non-surgical complication, including 3 cases (1.4%) of pulmonary infection and 1 (0.5%) of cardiovascular event. The patient with peritoneal hemorrhage was healed after re-operation and all other patients were discharged uneventfully after conservative treatment. Four cases (1.9%) developed complications beyond grade III a of Clavien-Dindo criteria. Conclusion Reinforcement on duodenal stump using laparoscopic single purse-string suture during laparoscopic radical gastrectomy with Roux-en-Y or Billroth II reconstruction is simple and effective, and can prevent the risk of development of duodenal stump leakage.