Objective:To explore the application of "upgraded single-entry colonoscope training method" in the primary endoscopic training of refresher doctors.Methods:A total of 71 refresher doctors who participated in the primary single endoscopy training in the Endoscopy Center of the Affiliated Hospital of Qingdao University from January 2017 to December 2019 were randomized to two groups: upgraded single-entry endoscopy training group ( n=36) and traditional single-entry endoscopy training group ( n=35). In the first week of training, all the participants learned the basic theory of single-entry enteroscopy insertion. From week 2 to week 11, each doctors of the two groups finally completed 80 to 100 cases of single-entry endoscopy. The upgraded single-entry colonoscopy training group was divided into two stages: "rectum-proximal sigmoid colon" and "descending colon-ileocecal part" with the boundary of descending-sigmoid colon as the dividing point, which was different from the traditional group. At the 12th week, each doctors were assessed by 20 cases of single-entry colonoscopy operation. the success rate of ileocecum insertion, the time to pass through sigmoid colon, the rate of loop formation and the average operation time of successful ileocecum insertion were compared between the two groups. SPSS 26.0 was used for t test or chi-square test. Results:Compared with the traditional single-entry endoscopy training group, the upgraded single-entry endoscopy training group achieved better results in the successful rate of ileocecal insertion (66.8% vs. 59.0%, P=0.005), the time to pass sigmoid colon [(6.05±3.32) min vs. (7.15±3.12) min, P<0.001], the loop rate (35.13% vs. 40.71%, P=0.035), the average operation time of successfully inserting the ileocecal part [(9.01±2.12) min vs. (10.25±3.12) min, P<0.001] and the discomfort response score [(5.19±1.41) vs. (6.70±2.15), P<0.001], with statistical significance between the groups. Conclusion:"Upgraded single-entry endoscopy training method" emphasizes no loop through sigmoid colon, which is more helpful for refresher doctors to master the operation skills of single-entry colonoscopy, shorten the teaching time, and reduce the discomfort of patients, and is suitable for popularization in the teaching.