Abstract: Objective To investigate the effect of "1 plus 2" oral administration with polyethylene glycol on intestinal preparation of colonoscopy in patients with chronic constipation. Methods Totally 120 chronic constipation patients with colonoscopy were selected and randomly divided into control group and observation group, with 60 cases in each group. The control group was prepared by traditional oral administration of polyethylene glycol, while the observation group was prepared by "1 plus 2" oral administration with polyethylene glycol. Boston Bowel Preparation Scale(BBPS)was used to evaluate the effect of intestinal cleaning and the condition of intestinal air bubbles, and the incidence of adverse reactions and acceptance rate of intestinal preparation were compared between the two groups. Results The BBPS score of the observation group was(8.30±0.81)points, which was significantly higher than(7.60±0.89)points of the control group(P<0.01). The intestinal air bubble score of the observation group was(0.32±0.54)points, which was significantly lower than(0.57±0.62)points of the control group(P<0.01). The incidence rate of nausea, vomiting, abdominal pain, abdominal distention, dizziness and hypoglycemia in the observation group was significantly lower than that in the control group(P<0.05 or P<0.01). The acceptance rate of intestinal preparation in the observation group was 66.67%, which was significantly higher than 41.67% in the control group(P<0.01). Conclusion For chronic constipation patients with - intestinal preparation by colonoscopy, polyethylene glycol “1 plus 2”administration is better than the traditional oral administration, which can effectively improve the efficiency of intestinal cleaning, relieve the discomfort degree, reduce the incidence of adverse reactions, and enhance the compliance and tolerance of patients.