Objective To study the effects of simple portal hypertension on the endotoxin levels in serum and intestinal mucosa of rats. Methods A total of 16 rats were divided into the blank control group (4 rats) and the model groups (3-day group, 7-day group and 10-day group, 4 rats in each group). The rat model of partial portal vein ligation was established in the model groups, and samples of blood and jejunum, ileum and colon of the rats were taken on the 3rd, 7th and 10th days, respectively. Changes in the serum endotoxin levels were detected by ELISA. Histopathological changes of the intestinal tissues were examined by HE staining. Results The rat model of partial portal vein ligation was successfully established in all the model groups. The serum levels of endotoxin on the 3rd, 7th and 10th days in the model groups were not significantly different from that in the normal control group. Damages of different intestinal segments were not serious on the 3rd day after modeling. However, on the 7th day after modeling, there were some sowllen and damaged intestinal villi in the intestinal mucosa of each intestinal segment, and the connection between the epithelial cells and the lamina propria was broken, compared with that at 3 days after modeling. In addition, there were obvious damages in the intestinal mucosa and lamina propria on the 10th day, compared with that at 3 d and 7 d after modeling. Conclusions In the case of normal liver function, portal hypertension can cause intestinal mucosal damages within a short period of time, but the amount of endotoxin produced by intestine does not exceed the processing capacity of the liver and thus does not cause an increase in the serum endotoxin level.