Abstract: Objective To explore the value of red blood cell distribution width (RDW) in assessment of the severity of acute pancreatitis (AP). Methods This retrospective analysis was conducted among 527 patients with AP treated in our department from May, 2013 to May, 2016. According to the severity of the condition, the patients were classified into mild acute pancreatitis (MAP) group, moderately severe acute pancreatitis (MSAP) group and severe acute pancreatitis (SAP) group, with 105 subjects without AP as the control group. The demographic data and data of RDW were collected from all cases to evaluate the value of RDW in assessing the severity of AP in comparison with classic evaluation indicators glucose (Glu) and calcium (Ca). Results The patients with AP and the control subjects showed significant differences in RDW, Glu and Ca (P<0.05). RDW and Glu was significantly higher but Ca was significantly lower in SAP patients than in MAP and MSAP patients (P<0.05). Binary classification logistic regression analysis showed that Glu (P<0.05, OR=2.343), Ca (P<0.05, OR=2.182) and RDW (P<0.05, OR=3.374) were all independent risk factors for AP. The area under the ROC curve for predicting SAP decreased in the order of RDW (0.801), Glu (0.658), and Ca (0.227). Conclusion RDW is a useful indicator for evaluation of the severity of AP.