Objective To investigate the value of acute pancreatitis severity bedside index(BISAP)score,monocyte to lymphocyte ratio(MLR),and neutrophil to albumin ratio(NAR)in the severity and prognosis of acute pancreatitis(AP).Methods The clinical data of 208 patients with acute pancreatitis admitted to the Affiliated Hospital of Southwest Medical University from January 2022 to December 2023 were retrospectively collected and divided into mild(MAP,n=131 cases)and severe(SAP,n=77 cases)groups according to the severity of the disease.Spearman correlation test was used to analyze the relationship between BISAP score,MLR,NAR and severity of disease and hospitalization days,and subject operating curve(ROC curve)analyzes the clinical significance of the above indicators in the prognosis of AP patients.Results The number of hospitalization days,BISAP score,MLR,NAR,WBC,PCT,FPG,TC,and Ca+were greater in the SAP group than in the MAP group,differences were statistically significant(P＜0.05);while the differences in Comorbidities,etiology,history of smoking,history of alcohol consumption,TC、TG、Ceea、GFR were not statistically significant(P＞0.05).By correlation analysis,the BISAP score,MLR and NAR were positively correlated with the severity of the disease(r=0.474、0.542、0.519)and the number of hospitalization days(r=0.401、0.370、0.396),differences were statistically significant(P＜0.05).Binary Loginstic regression showed that BISAP score,MLR,NAR,and FPG were all risk factors affecting patient prognosis.ROC curve analysis of BISAP score,MLR,and NAR were predictive of poor prognosis in AP patients(AUC=0.766、0.825、0.808),the combined predictive effect of the three was greater than that of a single index(AUC=0.863).Conclusion The number of hospitalization days,BISAP score,MLR,NAR,WBC,PCT,FPG,TC,and Ca+were greater in the SAP group than in the MAP group,differences were statistically significant(P＜0.05);while the differences in Comorbidities,etiology,history of smoking,history of alcohol consumption,TC、TG、Ceea、GFR were not statistically significant(P＞0.05).By correlation analysis,the BISAP score,MLR and NAR were positively correlated with the severity of the disease(r=0.474、0.542、0.519)and the number of hospitalization days(r=0.401、0.370、0.396),differences were statistically significant(P＜0.05).Binary Loginstic regression showed that BISAP score,MLR,NAR,and FPG were all risk factors affecting patient prognosis.ROC curve analysis of BISAP score,MLR,and NAR were predictive of poor prognosis in AP patients(AUC=0.766、0.825、0.808),the combined predictive effect of the three was greater than that of a single index(AUC=0.863).