Objective To explore the predictive value of bedsideindexfor severity in acute pancreatitis(BISAP) score combined with red blood cell volume distribution width (RDW) /Ca2+ on the disease severity in patients with early acute pancreatitis (AP). Methods The clinical data of 142 patients with early AP in the hospital were retrospectively analyzed. According to the severity of disease, the patients were divided into mild AP (MAP) group(n=87), moderate-to-severe AP (MSAP) group(n=31) and severe AP (SAP) group(n=24). Blood routine examination, blood calcium examination and BISAP score were performed within 24 hours after admission. The general data were compared among the three groups, and multivariate Logistic regression analysis was used to analyze the risk factors affecting the severity of early AP. Receiver operating characteristic (ROC) curve was applied to evaluate the value of BISAP score and RDW/Ca2+ alone and in combination in diagnosing the severity of early AP. Results There were no statistical differences in general clinical data among the three groups (P＞0.05). There were statistically significant differences in serum CRP, Scr, LDH, Ca2+, NLR, RDW, RDW/Ca2+ and BISAP score among the three groups (P＜0.05), but there were no statisticaldifferences in white blood cell, red blood cell, ALB, BUN, AST and ALT (P＞0.05). Multivariate Logistic regression analysis showed that serum CRP, NLR, RDW, blood Ca2+, RDW/Ca2+ and BISAP score were risk factors for the severity of patients with early AP (P＜0.05). ROC curve analysis revealed that the AUCs of BISAP score, RDW/Ca2+ alone and in combination for predicting the severity of patients with early APwere 0.835, 0.829 and 0.917 respectively, and the sensitivities were 81.82%, 78.16% and 87.27% and the specificities were 68.97%, 74.71% and 75.86% respectively. Combined diagnosis had high value.Conclusion BISAP score combined with RDW/Ca2+ detection can predict the severity and prognosis of patients with early AP, and the combined diagnosis has highpredictive value