Abstract: Objective To observe the pathological changes of the intestinal mucosa in rats with severe abdominal infection. Method A total of 60 SD rats were divided randomly into control group and experimental group (n=30), and in the latter group, the rats underwent cecal ligation and puncture (CLP) while those in the former had only laparotomy. The jejunum and ileum were sampled on postoperative days 1, 2 and 4 for optical and electron microscopic observations. The positivity rate of blood bacterial culture and plasma level of endotoxin were determined in the rats. Results No abnormal changes were observed with either optical and electron microscope in the small intestinal mucous membrane of rats in the control group, but in rats of the experimental group, microscopic examination revealed interstitial edema, vascular engorgement and neutrophil infiltration in the small intestine mucous membrane and the submucosa, and electron microscopy demonstrated loose and disorderly arrangement of the microvilli of the intestinal epithelium. Plasma endotoxin level in rats in the experimental group was 5- to 12-fold higher than that in the control group. The positivity rates of blood bacterial culture were 20%, 30% and 10% on postoperative days 1, 2 and 4 respectively in the experimental group, but were all zero in the control group. Conclusion Pathologic lesions in the intestinal mucosa occur during the early stage of severe abdominal infection in rats as the result of bacteria and endotoxin translocation.