Objective To evaluate the clinical value of bedside index for severity in acute pancreatitis (BISAP) and APACHEⅡ score in predicting the severity and organ failure of acute pancreatitis (AP).Methods One hundred eighty-five patients of AP admitted to Department of Gastroenterology of First affiliated Hospital of Soochow University from January 2012 to December 2014 were studied retrospectively.According to BISAP score, patients who were ≥3 points were considered as high risk group, while ＜3 points were considered as low risk group.According to APACHEⅡ score, patients who were ≥ 8 points were considered as high risk group, while ＜ 8 points were considered as low risk group.According to the criteria of Pancreatic Diseases Group of Chinese Society of Gastroenterology of Chinese Medical Association, the patients were diagnosed as mild acute pancreatitis (MAP), moderately severe acute pancreatitis (MSAP), and severe acute pancreatitis (SAP).The BISAP, APACHEⅡ scores were calculated and compared between MAP group and MSAP + SAP group, respectively.The incidence of MSAP + SAP between high risk group and low risk group was also compared.The area of ROC curve (AUC) was used to evaluate the ability of BISAP and APACHEⅡ scoring system for predicting the severity of AP and the multiple organ dysfunction syndromes (MODS).Results Among 185 patients, MAP was identified in 101 patients, MSAP in 76 patients and SAP in 8 patients.Twenty-five MSAP patients developed organ dysfunction, and all the 8 SAP patients developed organ dysfunction.The BISAP scores of MSAP + SAP group and MAP group were (1.43 ± 0.89), (0.38 ± 0.61),andAPACHⅡ scores were (2.45± 1.36), (0.87± 0.62), the scores of MSAP+ SAP group were significantly higher than those in MAP group (P ＜0.01).In the 137 patients of low risk BISAP group, there were 47 MSAP + SAP patients (34.3％), while in the 48 patients of high risk BISAP group, there were 37 MSAP + SAP patients (77.0％);in the 153 patients of low risk APACHEⅡ group, there were 56 MSAP + SAP patients (36.6％), while in the 32 patients of high risk APACHEⅡ group, there were 28 MSAP + SAP patients (87.5％);the incidence of MSAP + SAP patients was significantly higher in high risk group than that in low risk group (P＜0.01).The AUC of BISAP, APACHEⅡ for MSAP+ MAP was 0.804 (95％ CI 0.738 ～ 0.870), 0.794 (95％ CI 0.725 ～ 0.863), and the AUC for organ dysfunction was 0.758 (95％ CI 0.686 ～0.830), 0.781 (95％ CI 0.710 ～0.852) , and the difference between BISAP and APACHE Ⅱ was not statistically significant (P ＞ 0.05).Conclusions The BISAP has the prediction ability for AP severity and prognosis similar to APACHEⅡ , and it consists of only 5 parameters and can be completed in the first 24 h of admission, therefore it is worth of clinical application.