Pathogen inflection could induce specific immune response which will results in immunopathology when overreacted. Severe complications arising from influenza virus infection (pandemic influenza or the highly pathogenic avian H5N1viruses) are often associated with rapid, massive inflammatory cell infiltration, acute respiratory distress, reactive hemophagocytosis and multiple organ involvement. Histological and pathological studies show that a critical role for an excessive host response in mediating this pathology. Generally, the same imflammatory factors mediating tissue damage during the anti-influenza immune response are also essential for efficient elimination of virus. It was discussed how various effector arms of immune system can act deleteriously to initiate or exacerbate pathological damage in this viral infection. It will be helpful to understand the protective mechanism of influenza virus infection and a significant challenge in the design of harmless yet effective therapeutic strategies for tackling influenza virus.