BACKGROUND: To investigate the effect of enteral nutrition (EN) on intra-abdominal pressure (IAP) in severe acute pancreatitis (SAP) patients and the relationship between the decreasion of IAP and the the therapeutic effect of EN. METHODS: Eighty SAP patients were randomly divided into study group and control group (40 patients in each group). Patients in the study group received EN and Patients in the control group received total parenteral nutrition (TPN) for 7 days. Intra-cystic pressure (ICP) of the two groups was measured during treatment period. The outcomes of treatment were observed, APACHE Ⅱ scores, NB data were applied in analysis. RESULTS: The ICP data was lower in the study group than in the control group on days 4 and 5 of treatment (P < 0.05). On days 3-5 of treatment, the APACHE Ⅱ scores of the study group were lower than which of the control group (P < 0.05). Nitrogen balance (NB) date increased significantly in study group than in the control group (P < 0.05). abdominalgia relief time, operation rate were different between the two groups (P < 0.05). The abdominal compartment syndrome (ACS) occurrence rate of the two groups have no significant difference. The ICP data and APACHE Ⅱscores, abdominalgia relief time, operation rate of pancreas debridement show positive correlation (P < 0.05). ICP and NB date show negative correlation (P < 0.05). CONCLUSION: EN can decrease the IAP of SAP, which may be the reason for EN show preventive and therapeutic effects on SAP.