The aim of this study was to investigate the early changes in coagulation functions in patients with different degrees of Acute Pancreatitis (AP). Data from a total of 133 AP patients was studied. The differences in the Prothrombin Time (PT), Activated Partial Thromboplastin Time (APTT), Fibrinogen Concentration (FIB), International Normalized Ratio (INR), and serum Ca2+ levels among different groups, and their relationships to the Acute Physiology and Chronic Health Evaluation (APACHE) II score were compared. FIB in the Moderately Severe Acute Pancreatitis (MSAP) group was significantly higher than the Control Group (CG), and the Mild Acute Pancreatitis (MAP) group (P<0.05). Ca2+ levels in the MSAP group were lower than in the control and MAP groups (P<0.05). PT, APTT, and INR in the Severe Acute Pancreatitis (SAP) group were higher than in the control, MAP, and MSAP groups (P<0.05). FIB in the SAP group was higher than in the control and MAP groups (P<0.05), and Ca2+ levels in the SAP group were lower than in the control, MAP, and MSAP groups (P<0.05). The APACHE II score in the MSAP group was higher than in the MAP and control groups (P<0.05), and higher in the SAP group than in the MSAP, MAP, and control groups (P<0.05). Ca2+ levels and the APACHE II score were negatively correlated in the MSAP group. In the SAP group, FIB was positively correlated with the APACHE II score, but Ca2+ levels were negatively correlated with them. In the classification of acute pancreatitis, FIB and Ca2+ levels are associated with the severity of pancreatitis. Patients with early AP show different levels of coagulation dysfunction, which is much more pronounced in patients with MSAP and SAP.