Subclavian artery steal syndrome refers to the narrowing or occlusion of the subclavian artery or unnamed artery in the proximal segment of the beginning of the vertebral artery, after which the blood flow from the contralateral vertebral artery returns through the basilar artery to the affected vertebral artery to recompose the blood supply to the distal segment of the affected subclavian artery. 1, atherosclerotic Mainly seen in middle-aged and elderly people, there are mostly atherosclerotic risk factors of hypertension, diabetes mellitus, hyperlipidemia and smoking, which is a kind of systemic vascular damage. Subclavian or head and arm stem atherosclerosis is often accompanied by the same damage in other vessels in the extracranial neck. 2.Specific or non-specific arteritis Multiple aortitis is common, and its head and neck type can accumulate in the head and arm trunk and the beginning of the subclavian artery, resulting in lumen narrowing or occlusion. 3.Congenital It is caused by hypoplastic subclavian artery during fetal period, often accompanied by malformation of other parts such as heart and aorta. 4.Medical origin If the right subclavian artery starts from the aorta and presses on the esophagus causing difficulty in swallowing, it can cause this syndrome when vascular surgery is performed to correct it. 5.Traumatic Injury to the chest caused by a car accident can cause contusive thrombosis on the proximal side of the beginning of the vertebral artery of the subclavian artery, resulting in luminal narrowing or occlusion. 6.Other Such as rheumatic heart disease complicating the first segment of the left subclavian artery embolism, metastatic cancer embolism, etc.