To investigate the correlation of serum pentraxin 3 (PTX-3), soluble interleukin-2 receptor (SIL-2R), C-reactive protein (CRP), procalcitonin (PCT) levels, and acute physiology and chronic health evaluation II (APACHE II) scores in patients with severe acute pancreatitis (SAP). A total of 30 patients with SAP from October 2020 to October 2021 were selected as the SAP group, and 42 patients with mild acute pancreatitis (MAP) or moderate-severe acute pancreatitis (MSAP) was selected as the control group. The serum levels of PTX-3, SIL-2R, CRP, PCT, and APACHE II scores were evaluated. The serum levels of PTX-3, SIL-2R, CRP, PCT, and APACHE II scores at admission in the SAP group were significantly higher than those in the control group (all P < .05). Spearman analysis showed that serum PTX-3, SIL-2R, CRP, and PCT levels were positively correlated with APACHE II scores (all P < .05). The mortality rate within 28 days was 26.7% in the SAP group; moreover, the serum PTX-3, SIL-2R, CRP, and PCT levels and APACHE II scores at admission in the death group were significantly higher than those in the survival group (all P < .05). The receiver operating curve showed that the combined prediction value of all indicators (PTX-3 + SIL-2R + CRP + PCT + APACHE II) was superior to the single indicators, and the diagnostic sensitivity and specificity were 90.9% and 84.2%, respectively. Serum PTX-3, SIL-2R, CRP, and PCT levels and APACHE II scores have high guiding significance in early diagnosis and prognostic evaluation of SAP patients.Abbreviations: AP = acute pancreatitis, APACHE II = acute physiology and chronic health evaluation II, AUC = area under curve, CRP = C-reactive protein, MAP = mild acute pancreatitis, MSAP = moderate-severe acute pancreatitis, PCT = procalcitonin, PTX-3 = serum pentraxin 3, ROC = receiver operating characteristic, SAP = severe acute pancreatitis, SIL-2R = soluble interleukin-2 receptor.