Objective: To evaluate the effect of glucagonlike peptide-1 (GLP-1) receptor agonist liraglutide on the quality of bowel preparation for colonoscopy in patients with type 2 diabetes. Methods: A series of 195 patients with type 2 diabetes mellitus received oral hypoglycemic drugs combined liraglutide or insulin and underwent the first colonoscopy were prospectively enrolled from November 2014 to October 2017. The same split-dose 4 L polyethylene glycol was used for bowel cleansing. The Ottawa Bowel Preparation Scale (OBPS) and satisfactory bowel preparation (OBPS score of 6 or less) were used to assess the quality of bowel preparation. Results: In this series, 87 patients accepted oral hypoglycemic drugs combined liraglutide (the liraglutide group), and 108 patients accepted oral hypoglycemic drugs combined with insulin (the insulin group). The baseline data of the 2 groups were comparable (P>0.05). The OBPS scores (5.86±1.74 vs 5.54±1.81, t=1.270, P=0.206), and the satisfaction bowel preparation rate were similar (81.6% vs 82.4%, χ2=0.021, P=0.885) between the liraglutide group and the insulin groups (P>0.05). There were no hypoglycemic events in the 2 groups during the bowel preparation. Conclusion: The GLP-1 receptor agonist liraglutide has little effect on the quality of bowel preparation for colonoscopy in patients with diabetes mellitus.