Background: Recent studies showed that the clinical outcome of moderately severe acute pancreatitis (MSAP) are different among different subgroups. Aims: To further subdivide MSAP, and explore the heterogeneity of MSAP subgroups. Methods: A retrospective analysis was performed on patients with acute pancreatitis (AP) from January 2016 to December 2020 at Northern Jiangsu People’s Hospital, including 538 patients with mild acute pancreatitis (MAP) and 461 patients with MSAP. MSAP patients were divided into four groups according to local complication and transient organ failure (TOF), including single acute peripancreatic fluid collection (APFC) without TOF group (group A), multiple APFC without TOF group (group B), other local complication without TOF group (group C) and TOF group (group D). The baseline data and the severity of AP among the four subgroups were compared. Meanwhile, the severity of disease between group A and MAP patients was also compared. Logistic regression analysis was used to evaluate the risk factors of MSAP. Results: Patients in group D were older than those in group A (P<0.05). There were statistically significant differences in different scoring systems among the four subgroups (P<0.05). The proportions of APACHE Ⅱ≥8, Glasgow≥3 and BISAP≥3 in group D were significantly higher than those in the other three groups (P<0.05). There were significant differences in levels of Ca