Acute pancreatitis (AP) is an inflammatory disease of the pancreas. We analyzed changes in inflammation markers to explore the clinical significance of using these markers to predict the severity of AP. The study included 169 patients (severe AP = 50 and nonsevere AP = 119) admitted to Yanbian University Hospital between January 2015 and July 2017. The neutrophil-to-lymphocyte ratio (NLR), prognostic nutrition index (PNI), lymphocyte-to-monocyte ratio, red blood cell distribution width coefficient of variation, mean platelet volume, platelet-to-lymphocyte ratio, and red blood cell distribution width-to-platelet ratio of the patients were detected after admission. Correlations between AP severity and various inflammatory markers were statistically analyzed. The results indicated that the NLR on the first day after admission (area under the curve, 0.824; 95% confidence interval, 0.753-0.896) and the PNI on the third day after admission (area under the curve, 0.814; 95% confidence interval, 0.753-0.896) had more significance than other inflammation markers in predicting the severity of AP. In AP patients, the NLR showed a gradual decline, and the PNI initially decreased and then increased. The NLR and PNI can provide new reference values for predicting the severity of AP.