Abstract: Objective To explore the effect of oral administration versus direct enteral injection of same dose of simethicone emulsion on mucosal visualization at colonoscopy. Methods One hundred patients who underwent colonoscopy in our hospital from May 2016 to May 2017 were enrolled in the study, and they were randomly divided into two groups with 50 cases in each group.Patients in the control group received oral administration of 30 mL of simethicone emulsion at 4 hours before examination, and in the experimental group, 30 mL of simethicone emulsion was dissolved in 500 mL of normal saline and injected into the intestine directly.The bowel cleanliness, mucosal visibility score and the detection rate of polyp were compared between two groups. Results Overall cleansing (excellent or good) quality was significantly higher in the observation group compared to control group (84% vs 64%, P=0.023). The effect of eliminating foam and bubbles in the observation group was better than that in the control group. There was no significant difference in bowel cleanliness (72% vs 76%) and detection rate of polyp in the intestine (46% vs 32%) between the two groups (P> 0.05, respectively). Conclusion Simethicone emulsion diluting directly into the intestine can provide a clearer inspection fi eld compared to oral administration of the same dose, which is worthy of clinical application.