Postoperative cognitive dysfunction（POCD）is a common postoperative complication in elder people after surgery，and it’s main clinical manifestations are changes in personality, social ability and cognitive ability. Which not only prolongs hospital stays, increases the cost of treatment and burden on society，but also affects the quality of life of patient severely. The mechanism of POCD is still unclear. There are many hypotheses, and the hypothesis of central nervous system inflammation is gradually recognized by more people. In recent years, a large number of studies have shown that the development of postoperative cognitive dysfunction is closely related to surgery and anesthesia, but the influence of depth of anesthesia on postoperative cognitive dysfunction remains controversial. This article is aim to discuss the definition of depth of anesthesia，the effect of different depth of anesthesia on the occurrence of POCD and possible mechanism of the influence of depth of anesthesia on POCD.