Backgroud Postoperative delirium, a common complication of elderly patients, frequently occurs 24~72 hours after surgery. Though the pathophysiology of delirium is complex and not well known, studies have shown that inflammatory responses in the central nervous system may play an important role. Objective To explore the neuroinflammation mechanism of postoperative delirium, and provide a theoretical basis for its prevention. Content In this paper, we discussed how the peripheral inflammation leads to neuroinflammation and how the inflammatory cytokines TNF-α, IL-1β, IL-6 and S100β protein play a clinical effect and the cerebral protective effect of ulinastatin and so on. Trend Providing a new idea for the prevention of postoperative delirium and clinical application of ulinastatin .