The use of mannitol after cerebral infarction, most patients with cerebral infarction are given mannitol 24 hours after the onset of the disease, and the application time is about 5 days. Because the peak edema of most patients with cerebral infarction is on the 3rd-5th day of onset, the main purpose of giving mannitol to patients is to reduce intracranial pressure and decrease cerebral edema to avoid brain herniation. If the patient has a large cerebral infarction and the edema is more serious, the patient should be given mannitol during the acute onset to avoid brain herniation. Mannitol is mainly used to dehydrate and lower intracranial pressure. Patients are advised to monitor blood pressure, urine volume and serum ions during the application of mannitol to avoid electrolyte disorders or low blood pressure, which may aggravate cerebral ischemia. Mannitol is applied for 3-5 days, and in some patients with large cerebral infarction it can be applied for 7-14 days.