Objective: To evaluate the effects of lactulose for bowel preparation prior to colonoscopy in adults. Methods: By searching for literature pertaining to RCT (randomized controlled trial) of bowel preparation with lactulose in adults up to 10th of July, 2021. The experimental group utilizes lactulose oral solution as the solution of choice for bowel preparation while the control group uses the standard bowel preparation solution. Literature selection and data extraction were completed independently by 2 researchers, including literature quality control. Data analysis was completed using the software RevMan5.2. Results: 11 RCT was included for data analysis. Meta-analysis showed that the lactulose group had a lower incidence of adverse effects [OR=13.58, 95CI% (6.10, 30.24), p<0.0001] and better tolerability [OR=13.58, 95CI% (6.10,30.24), p<0.0001] when compared with the control group. However, the bowel cleanliness was statistically insignificant between the two groups [WMD=0.26，95%CI (-0.31，0.82), p=0.38]. Conclusion: according to current evidences, as a solution for bower preparation, lactulose has a lower incidence of adverse effects such as emesis or diarrhea, while effectively increasing tolerability, however it is not a superior solution for bowel preparation in terms of bowel cleanliness when compared with other standard choices. More high quality researches will be required to support its use.