To evaluate the effects of early-phase drainage on the survival rates and pancreatic pathological changes associated with severe acute pancreatitis (SAP) in a rat model. Sprague-Dawley rats were divided into the following groups: SAP model (control), early drainage and delayed drainage. The 24-h survival rates were compared among the groups. In addition, the serum and ascites concentrations of interleukin (IL)-1 beta, IL-6, IL-8, IL-10 and tumor necrosis factor (TNF)-alpha were measured, and pancreatic pathological changes were observed. The survival rate significantly improved in the early drainage group. Compared with that observed in the control group, the serum TNF-alpha and IL-8 concentrations in the early drainage group decreased, while the serum IL-10 levels increased, and the ascites concentrations of IL-1 beta, IL-6, IL-8 and TNF-alpha decreased, while that of IL-10 increased significantly. In the delayed drainage group, only the ascites concentrations of TNF-alpha decreased. Meanwhile, the pancreatic pathological changes at 3, 6 and 24 h worsened in the early drainage group; however, the pancreatic lesions in the early drainage group were less mild than those seen in the control group. Rebalancing the cytokine levels in ascites after early drainage may be a key factor for enhancing the survival rate in rats.