BACKGROUND Ulinastatin is a protease inhibitor derived from urine that has shown anti-inflammatory effects in human disease, including in sepsis. Necrotizing enterocolitis (NEC) is a common gastrointestinal disease in premature infants. Our aim was to explore the effects of ulinastatin on a neonatal NEC rat model. MATERIAL AND METHODS Forty-five neonatal rats were divided into 3 groups: normal control; NEC+sepsis-induced kidney injury (SIRS); NEC/SIRS+ulinastatin. The NEC/SIRS model was induced by injection of intraperitoneal saline, enteral formula feeding, hypoxia-hyperoxide, and cold stress exposure. The NEC/SIRS neonatal rats were perfused with ulinastatin at a dose of 10 000 u/kg/day. Giemsa staining and hematoxylin and eosin (H&E) were performed to evaluate the severity of intestinal damage. To assess intestinal cell apoptosis, we examined the expression of caspase-3 by TUNEL staining and western blot analysis. Intestinal levels of inflammatory cytokines (IL-1ß, IL-6, and TNF-alpha) were examined using ELISA assay. RESULTS Rats in the NEC treated with ulinastatin group had better physiological status and histological score compared to the NEC/SIRS group. Ulinastatin reduced NEC-induced weight loss. Macroscopic and microscopic morphology analyses showed that rats in the NEC treated with ulinastatin group had lower severity of intestinal damage compared to the NEC/SIRS group. TUNEL staining and caspase-3 expression detection results revealed that ulinastatin significantly inhibited intestinal cell apoptosis of NEC. Furthermore, ulinastatin decreased the intestinal levels of IL-1ß, IL-6, and TNF-alpha in NEC. CONCLUSIONS Ulinastatin could ameliorate the severity of intestinal damage in NEC and possess anti-apoptosis and anti-inflammation effects.