Cerebrovascular blood flow test refers to transcranial color Doppler ultrasound, which is mainly designed to explore the condition of intracranial blood vessels, including the size of the lumen of the blood vessels, the degree of stenosis, the presence of atherosclerosis and plaque formation, the presence of vascular occlusion, and can find out whether the distribution of the large blood vessels is reasonable, and whether there are any vascular malformations including cavernous hemangiomas, arteriovenous malformations, and so on. It can also monitor the velocity of blood flow and indirectly find out whether there is any abnormality in the lumen of blood vessels. If the patient has embolic rain, there are other parts of the thrombus dislodged, the formation of small thrombus, in the operation of blood flow, through this test can also be found, can be used as a kind of assessment of cerebrovascular function as well as the incidence of cerebral infarction indicator. If the patient is in the acute phase of cerebrovascular disease, perfecting this test can help determine the subsequent treatment plan and clarify the indications for secondary prevention.