Objective To investigate the effect of capsule endoscopy on the small intestinal mucosa in the state of air insufflation. Methods Patients undergoing capsule endoscopy from November 2011 to April 2012 were divided into the air insufflation intervention group ( n＝14) and routine examination group (n＝13) by random number table method. The detection rate of small bowel disease, the transit time of capsule endoscope in small intestine, the degree of intestinal cleaning and the degree of intestinal lumen expansion were compared between two groups. Results There was no significant difference in total intestinal examination rate [ 85. 71%( 12/14) VS 61. 54%( 8/13),P＝0. 209] or disease detection rate [ 71. 43%(10/14) VS 84. 62%( 11/13), P＞0. 05] between air insufflation intervention group and conventional examination group. The mean procedure time of the air insufflation intervention group was 270. 86 ± 144. 85 min, which was shorter than that of the conventional examination group (325. 15±161. 76 min, P＝0. 369). The overall cleanliness of the air insufflation intervention group was higher than that of the conventional examination group (2. 05±0. 40 VS 1. 75±0. 40,P＝0. 060). The overall degrees of expansion of small intestine lumen were 1. 79 ± 0. 40 and 1. 38 ± 0. 29 scores, respectively ( P ＝ 0. 004 ). Conclusion Capsule endoscopy can significantly improve the degree of intestinal lumen expansion with trend of improving the overall cleanliness of the small intestine, and shortening the working time of the small intestine.