Objective:To analyze the intestinal preparation effect of dimethicone oil combined with polyethylene glycol electrolyte powder in painless gastrointestinal endoscopy.Methods:The study included 380 patients undergoing painless gastrointestinal endoscopy in Nanjing Qixia District Hospital from January 2020 to June 2021. They were randomly grouped into observation group and control group, with 190 patients in each group. The control group was given polyethylene glycol electrolyte powder + 0.9% sodium chloride for intestinal preparation before gastrointestinal endoscopy, and the observation group was given polyethylene glycol electrolyte powder + dimethicone silicone oil. The intestinal cleanliness, antifoam effect, colonoscopy index, detection rate of polyps, adenomas and advanced adenomas, and adverse drug reactions were compared between the two groups.Results:The satisfaction rates of intestinal cleaning and defoaming in the observation group were 92.11% (175/190) and 90.53% (172/190) respectively, which were obviously higher than those in the control group: 84.71% (161/190) and 83.16% (158/190) ( P>0.05). The entering time of colonoscopy and the time of colonoscopy inspection in the observation group were obviously shorter than those in the control group: (3.35 ± 1.05) min vs. (6.02 ± 1.68) min, (11.86 ± 1.93) min vs. (15.22 ± 2.10) min. The rinsing amount of 0.9% sodium chloride was obviously reduced: (35.68 ± 7.64) ml vs. (50.34 ± 10.30) ml ( P<0.05). The detection rate of <5 mm polyps in the observation group was obviously higher than that in the control group: 15.79% (30/190) vs. 5.79% (11/190) ( P<0.05). The detection rate of adenomas in the observation group was obviously higher than that in the control group: 24.74% (47/190) vs. 15.79% (30/190) ( P<0.05). The detection rate of advanced adenomas in the observation group was obviously higher than that in the control group: 20.53% (39/190) vs. 9.47% (18/190) ( P<0.05). The total incidences of abdominal distension and adverse reactions in the observation group were obviously lower than those in the control group: 1.05% (2/190) vs. 5.26% (10/190), 9.47% (18/190) vs. 18.42% (35/190) ( P<0.05). Conclusions:The application of polyethylene glycol electrolyte powder combined with dimethicone oil in painless gastrointestinal endoscopy can effectively improve the intestinal cleanliness, the satisfaction of removing bubbles and the detection rate of polyps and adenomas, reduce the incidence of adverse reactions, and have high clinical application value.