【Abstract】 Background Postoperative delirium refers to a acute neuropsychiatric syndrome characterized by inattention and cognitive dysfunction. The elderly seem to experience a greater chance. Multifactor cause the complex cognitive and behavioral changes observed in delirium. To date, pathogenesis and pathophysiology of delirium remain elusive. Objective This review focus on the mechanism of postoperative delirium. Content This article includes hypotheses of inflammatory cytokines, neuroendocrine, neurotransmitter, biological rhythm, aging and so on to calrify the pathogenesis of delirium. Trend With the intensive study of postoperative delirium,more and more mechanisms and pathologic processes will be found to provide new theories for effective prophylaxis and treatment of delirium in clinical.