To investigate patients with severe acute pancreatitis (SAP) by dynamic levels of pro-/anti-inflammatory cytokines and endotoxin (ET) in plasma and the relationship between immunity and infection, organ dysfunction. Seventy-two patients with SAP were recruited. The ET, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), and interleukin-4 (IL-4) were determined on admission and days 3, 7, and 14. For comparison, patients were analyzed through infection group versus non-infection group, multiple organ dysfunction syndrome (MODS) group versus non-MODS group. There were sixteen patients with secondary infection, twenty-two with MODS, and nine deaths. The infection group had higher levels of ET than the non-infection group on days 3 and 7. The dynamic cytokine levels of patients in the MODS group were unanimous with those outcomes in the infection group. The levels of cytokines in the infection group were different from the non-infection group, with more levels of TNF-α, IL-6 on days 3 and 7 and less on days 14, and more levels of IL-10, IL-4 on days 7 and 14. The levels of TNF-α, IL-6 in the MODS group were different from the non-MODS group, with more levels on days 3 and 7, and less levels on days 14. Immune dysregulation may play an important role in infection and organ dysfunction for patients with SAP.