Abstract： Objective： To observe the curative effect of umbilical application with Tongbian San combined with polyethylene glycol electrolyte on bowel preparation before colonoscopy. Methods：A total of 100 cases of patients who underwent colonoscopy were selected as the research subjects and randomly divided into the control group and the observation group， with 50 cases in each group. The control group received pre-examination of bowel preparation with polyethylene glycol electrolyte， and the observation group received pre-examination of bowel preparation with application of umbilical application with Tongbian San combined with polyethylene glycol electrolyte. The defecation time， Boston Bowel Preparation Scale (BBPS) scores，intestinal bubble volume，and incidence of adverse reactions were compared between two groups. Results：After treatment，the first bowel movement and bowel emptying time in the observation group were shorter than those in the control group，the difference being significant (P＜0.05). The left and right colon，transverse colon cleanliness scores in BBPS in the observation group were higher than those in the control group，the difference being significant (P＜0.05). The grading of intestinal bubble volume in the observation group was better than that in the control group，the difference being significant (P＜0.05). The incidence of adverse reactions was 16.00% in the observation group，and 26.00% in the control group，the difference being significant (P＜0.05). Conclusion： The application of umbilical application with Tongbian San combined with polyethylene glycol electrolyte in bowel preparation before colonoscopy can promote defecation and improve intestinal cleanliness，which is beneficial for the progress of colonoscopy and has good safety.