Subclavian artery steal syndrome is due to a severe local stenosis or complete occlusive nature of the left subclavian artery or the proximal segment at the beginning of the vertebral artery of the cephalic trunk. Due to the siphoning effect, it causes the blood flow from the normal side of the vertebral artery to reverse to the affected vertebral artery to supply the patient’s limb, resulting in insufficient blood supply to the basilar artery, causing cerebral ischemic attacks such as dizziness, no pulse or weak pulse in the affected upper limb, reduced blood pressure, and numbness in the limb. Interventional treatment is to open the occluded vascular segment and implant a stent to keep the vessel open, restore the normal blood supply to the cerebellum and brainstem, and improve clinical symptoms. 1.CTA: occlusion of the left subclavian artery, segment is not visualized 2.CT: no blood flow in the occluded segment 3.Aortogram: left subclavian artery is not visualized 4.Late aortogram: left vertebral artery reverses flow to the subclavian artery 5.After opening the occluded segment, stent is delivered 6.Dilation of stent 7.After successful release of stent, the left subclavian artery is unobstructed and the blood flow of the left vertebral artery turns to normal towards the intracranial blood flow