〔Abstract〕 Objective To investigate the effect of hydrogel on oxidative stress and the protective effect of intestinal injury in rats after open abdomen. Methods A poly(ethylene glycol) modified with tyramine was grafted onto a chitosan backbone to enhance the solubility of the chitosan and to crosslink into three-dimensional networks. Followed by intraperitoneal injection of air to induce abdominal compartment syndrome, sixty rats were randomly divided into hydrogel group(CPT group), temporary abdominal closure group(TAC group) and sham operation group(Sham group). Hydrogel group was treated with chitosan-polyethylene-tyramine molecular hydrogel coated on the intestine, and then closed with a polypropylene mesh after open abdomen(CPT group). Temporary abdominal closure group was temporarily closed with a polypropylene mesh after open abdomen(TAC group). Sham group was undergone laparotomies and then closed immediately(Sham group). At immediately four hours after open abdomen,the oxidative stress cells in the small intestinal epithelium of the hydrogel group and the temporary abdominal closure group were detected by immunohistofluorescence. The levels of malondialdehyde( MDA) and 8-OHDG in intestinal homogenate of the three groups were measured at specific time points by TBA and ELISA respectively. Results At 4 h after open abdomen,no oxidative stress injury was observed in intestinal epithelial cells in the CPT group and oxidative stress injury of intestinal epithelial cells was observed in the TAC group. Four hours after open abdomen,MDA and 8-OHDG levels were significantly highest in the TAC group,followed by CPT group,with Sham group was the least. At 8 h and 24 h after open abdomen,MDA and 8-OHDG levels in CPT group returned to Sham values,whereas these levels in TAC group were higher than those of Sham group. Conclusion The biomaterial chitosan-polyethylene glycol-tyramine molecular hydrogels can significantly reduce oxidative stress levels and protect against intestinal damage in small intestine after open abdomen.