Objective To optimize and evaluate the effect of a patient education app for bowel preparation in patients undergoing colonoscopy. Methods A total of 421 patients who underwent colonoscopy were assigned to a control group of 209 and an intervention group of 212 chronologically.Patients in the control group received routine health education on bowel preparation, while their counterparts in the intervention group were asked to use an optimized education app for bowel preparation education. The app composing rich information sources, could remind patients at key time points, label those at high risk of bowel cleansing failure, and strengthen online patient-nurse communication. Bowel preparation quality and adverse reactions were compared between the two groups.Evaluation of the app was also investigated. Results The qualification rate of bowel preparation and the score of bowel cleansing quality were significantly higher, whereas the rates of vomiting and abdominal bloating were significantly lower in the intervention group compared with the control group （P＜0.05,P＜0.01）.Greater than eighty percent （84.4%） of patients in the intervention group believed the education app is helpful and user-friendly. Conclusion Optimizing an app for bowel preparation education can enhance bowel preparation quality and reduce adverse reactions.