Determinant-based classification (DBC) and revised Atlanta classification (RAC) are two new systems of acute pancreatitis (AP) severity classi.cation. The difference between them is in classification of moderate AP (MAP). Therefore, we aimed to explore the practical value of RAC and DBC systems in classifying MAP. A total of 321 patients with MAP were included and assigned to RAC (n = 167) and DBC (n = 154) groups. Each group was further divided into three subgroups: local complication only, transient organ failure only, and both. Outcome variables including in-hospital mortality, intensive care unit (ICU) admission, surgery for infected pancreatic necrosis (IPN), length of ICU stay and hospital stay were compared among the three subgroups in each group. Meantime, patients in the RAC group were divided into infected group and sterile group and possible predictors and risk factors for infection were investigated. No significant differences were observed in MAP patients characteristics between the two groups except in infected necrosis (P = 0.000). According to the MAP criterion of RAC, the ICU admission (P = 0.000), surgery for IPN (P = 0.000), and ICU stay (P = 0.012) were significantly different among the three subgroups. For the MAP criterion of DBC, no significant differences were found among the three subgroups. In addition, we found that (peri) pancreatic necrosis, Ranson score, CT score, and organ function failure were possible predictors and risk factors for patients with infection. RAC system has higher heterogeneity than DBC system when used to classify MAP.