Subarachnoid hemorrhage is divided into four phases, the clinical manifestations of which are different. First, the hemorrhagic phase, in which the onset of hemorrhage usually occurs within 24 hours, and some may extend to two weeks or even a month. At this time, the intracranial pressure is very high, and the patient can show sudden severe headache, nausea, vomiting, deepening of consciousness or convulsions, for example, the original symptoms and signs can be aggravated or new signs can reappear, such as sudden inability to speak and sudden hemiparesis. The diagnosis is mainly based on clinical manifestations and CT results, and if necessary, lumbar puncture is needed to check the cerebrospinal fluid. Second, it is the spastic phase of cerebrovascular. It is mainly manifested in altered consciousness, focal neurological impairment, such as hemiparesis and aphasia, and the symptoms of brain tissue damage near the aneurysm are usually the most serious. Thirdly, it is the hydrocephalus phase, and patients in this period are more mildly characterized by drowsiness, mental and motor retardation and memory impairment. In more severe cases, progressive mental and intellectual impairment, gait abnormalities and urinary and bowel disorders may occur. Some patients may experience pulmonary dysfunction, catecholamine fluctuations and sympathetic dysfunction.