In patients with mild subarachnoid hemorrhage, it takes about 2-3 weeks to pass the danger period, and no specific time can be given for the danger period in patients with severe subarachnoid hemorrhage. Common complications of subarachnoid hemorrhage include rebleeding, which occurs in about 20% of patients with aneurysms 10-14 days after onset, doubling the mortality rate; cerebral vasospasm, which begins 3-5 days after onset and peaks at 5-14 days with delayed cerebral vasospasm that gradually disappears in 2-4 weeks; and acute or subacute hydrocephalus due to subarachnoid hemorrhage, which occurs within 1 week of onset. In addition, acute or subacute hydrocephalus due to subarachnoid hemorrhage occurs within 1 week of onset. The overall prognosis of subarachnoid hemorrhage is poor, with a mortality rate of up to 45% and a high rate of disability in survivors. The prognosis is mainly related to the etiology, the site of bleeding, the amount of bleeding, and the presence of complications. Some patients who survive may have permanent disability, mainly cognitive impairment.