Objective To implement the best evidence of bowel preparation for colonoscopy in hospitalized patients and to evaluate the effectiveness of the evidence-based nursing protocol. Methods The process consisted of 4 steps including evidence acquisition，baseline evaluation，evidence introduction，and effect evaluation. An interrupted time series design was used to compare the effects of the evidence of bowel preparation before colonoscopy by medical staff before the practice（December 2019—May 2020） and after the practice（September 2020—November） on knowledge，performance rate of pre-colonoscopy bowel preparation review index and colonoscopy one-time success rate. Results We finally included 7 pieces of evidence in protocol. The score of evidence on bowel preparation for colonoscopy in medical staff increased from（73.49±6.50） to （80.88±6.27）（t=5.37，P<0.01）. The one-time success rate of colonoscopy increased from 95.54% to 97.61%（ χ²=1.33，P=0.25）. Conclusion The evidence-based practice can improve the performance of medical staff and standardize the process of bowel preparation.