Objective: To investigate the influences of enteral nutrition supports of different formulas on nutritional status, intestinal barrier function and systemic inflammatory responses in patients with severe acute pancreatitis (SAP). Methods: One-hundred and twenty SAP patients were equally randomized into 3 groups, and then underwent immune-enhancing enteral nutrition (IN group), elemental enteral nutrition (EN group) and ecological immune enteral nutrition (EIN group), respectively. The nutrition indicators, peripheral blood endotoxin concentrations and parameters of oxidative stress and inflammatory responses before and at 7 and 17 after treatment among the three groups were compared. Results: There was no statistical difference in any of the studied indexes among the three groups before treatment, which were all significantly improved after treatment and progressively with time (all P<0.05). Results of intergroup comparison showed that serum levels of hemoglobin, albumin, transferrin, prealbumin and levels of IL-10 and superoxide dismutase (SOD) were significantly higher, while the serum levels of diamine oxidase (DAO), endotoxins, malondialdehyde (MDA), high-sensitivity C-reactive protein (hs-CRP), IL-6 and TNF-α were significantly lower in EIN group than those in either IN group or EN group at 7 and 14 d after treatment (all P<0.05); all indexes at the same time point showed no statistical difference between IN and EN group (all P>0.05). Conclusion: For SAP patients, ecological immune enteral nutrition can effectively improve the nutritional status, protect intestinal barrier function, lower the levels of oxygen free radicals and serum endotoxins, so it is beneficial to improving the outcome and prognosis of these patients.