Background　Previous studies demonstrated that hemodilution can not cause significant damage to cerebral metabolism and functions. However， recent evidence showed that acute anemia induced by perioperative hemodilution can result in adverse effects on the brain.　Objective　This review discusses cerebral injury induced by acute anemia and its mechanisms， thus to provide theoretical basis for the rational application of intraoperative hemodilution technique.　Content　Acute anemia is associated with postoperative cognitive dysfunction， secondary post-traumatic brain injury and poor outcome of subarachnoid hemorrhage. The review also elaborates the role of NO synthase （NOS）， hypoxia-inducible factor （HIF）-1 alpha， HIF-responsive molecules and inflammatory cytokines in anemia-induced cerebral injury.　Trend　Acute anemia induced by hemodilution may have adverse effects on brain， optimizing this technique will improve outcome for those patients predisposing to cerebral injury.