Abstract: AIM To evaluate the effects of polyethylene glycol electrolyte powder combined with different agents in bowel preparation for colonoscopy examination in elderly constipation patients.METHODS A total of 108 elderly patients with constipation who would undergo bowel preparation for colonoscopy were enrolled from March 2016 to May 2017, and they were prospectively randomized into three groups: A, B, and C (n = 36 each). Patients of group A only took polyethylene glycol electrolyte powder, patients of group B took polyethylene glycol electrolytes powder combined with lactulose, and patients of group C took polyethylene glycol electrolytes powder combined with folium sennae. The colon cleaning quality, gastrointestinal complications, and patient compliance were evaluated. RESULTS The bowel preparation score of group B (7.96 ± 0.75, 94.3%) was better than those of groups A (5.11 ± 1.02, 66.7%) and C (5.83 ± 1.13, 22.2%), and the difference was statistically significant (P< 0.05). The rate of gastrointestinal complications in group B (2.7%, 8.3%) was much lower than that of group C (13.8%, 25%). No significant difference was observed in patient compliance between groups A (66.7%), B (63.8%) and C (55.6%).CONCLUSION Polyethylene glycol electrolyte powder combined withlactulose could improve the cleaning quality of bowel preparation in elderly patients with constipation and has no obvious gastrointestinal complications, representing a more effective and safer method for bowel preparation.