ObjectiveTo summarize progress of immune response in severe acute pancreatitis (SAP) and to provide a basis for appropriate immunotheraphy.MethodThe relevant literatures about the effect of immune response in the SAP with infectious complications in recent years were reviewed.ResultsThe inflammatory cascade reaction occurred in the early stage of SAP. Subsequently, the compensatory anti-inflammatory response syndrome (CARS) arised and immune response of the organism was suppressed. At this stage, the rate of infection was higher than before.ConclusionsCARS is one of major reasons in SAP with infectious complications. At present, fluid infusion, fasting, parenteral nutrition and like are major therapies in SAP. If corresponding immunotherapy could be carried out according to immune mechanism of SAP infection, that is, early appropriate immunosuppressive therapy and dynamic monitoring of body’s immune system state should be performed, when it is found that immunosuppression is present, appropriate immunostimulus therapy will be possible to reduce mortality of SAP and improve its prognosis.