Objective To evaluate the effect of the dimethicone powder in bowel preparation before capsule endoscopy （CE） and to observe its possible adverse effects. Methods A total of 60 patients receiving CE were prospectively randomized into 2 groups according to bowel preparation method. In dimethicone powder group, patients were arranged to take dimethicone powder 30 min before the examination on basis of macrogol electrolytes powder and in control group, patients had macrogol electrolytes powder only. Images of small intestine were equally divided into segments A, B and C according to intestinal transit time, and reviewed by 2 experienced physicians independently. Intraluminal gas bubbles were graded and any possible adverse effects were monitored. Results Interobserver agreement was excellent （P 〈 0. 05 ）. In segments A and C, images from dimethicone powder group were less interfered by gas bubble than those from control group （ P 〈 0. 05 ） , but in segment B there was no difference between 2 groups （ P 〉 0.05 ）. No adverse effects were observed. Conclusion The dimethicone powder administration before capsule endoscopy improves the visualization of the intestinal mucosa.