Abnormal blood glucose is one of the common problems during perioperative period. Eecently, numerous studies have demonstrated that postoperative cognitive dysfunction (POCD) is closely linked to perioperative dysglycemia. Perioperative dysglycemia events, including hyperglycemia and hypoglycemia, increase the risk of POCD. The influence of hyperglycemia on postoperative cognitive function may be caused by neuroinflammatory response, the change of blood‑brain barrier permeability and oxidative stress etc. Preventing occurence of hyperglycemia is an important measure to reduce POCD, but there is no uniform standard for the optimum perioperative blood glucose level. In addition, in order to avoid further damage to cognitive function due to hypoglycemia caused by intravenous insulin infusion, intranasal insulin infusion not only has no effect on the level of peripheral blood glucose, but also improves the cognitive function.