Objective：To explore the protective effects of recombinant human granulocyte-macrophage colony-stimulating factor （rhGM-CSF） on intestinal mucosal barrier in rats with severe acute pancreatitis. Methods：36 male SD rats were randomly and evenly divided into 3 groups：control group（sham operation group），severe acute pancreatitis model group（SAP group），and rhGM-CSF group（SAP rats treated with rhGM-CSF）. The SAP rat models were established via retrograde injection of 3% sodium taurocholate to the pancreatic duct. Rats in rhGM-CSF group were hypodermically injected with rhGM-CSF with dose of 3 ?滋g/kg per day for 5 days. All rats were executed on day 5，and the intestinal mucosal damage，the ratio of CD4+/CD8+ and the composition of intestinal flora were analyzed. Results：There was no death in rats with SAP，and obvious pathological changes appeared in the mucosa of both groups. Compared with SAP group，damage to intestinal mucosa of rats in rhGM-CSF group were significantly reduced，the epithelial cells were almost intact，the villi were closely arranged，the small intestine gland was deepened and the number was larger，the numbers of goblet cells and vascular endothelial cells were increased，and the mucosal thickness and intestinal wall edema were alleviated；The number of CD8+ lymphocytes in lamina propria was significantly reduced，and the CD4+/CD8+ ratio was obviously higher. The intestinal flora in SAP group changed evidently compared with control group. The content of Bifidobacteria and Lactobacilli of observation group were higher than those of SAP group[（6.34±4.64） ln/g vs. （3.71±4.96） ln/g，（9.52±3.86） ln/g vs. （5.17±2.14） ln/g，P<0.05]，while Escherichia coli and Enterococci were lower[（7.98±2.23） ln/g vs. （11.36±3.74） ln/g，（4.65±1.85） ln/g vs. （7.28±2.63） ln/g，P<0.05]. Conclusion：rhGM-CSF may improve effect of intestinal mucosal barrier in rats with severe acute pancreatitis.