Carotid artery is the main blood vessel supplying blood to the brain. Atherosclerotic plaque is a lesion of the arterial wall, which causes unsmoothness, wall thickening and lumen narrowing. The plaque is divided into soft plaque and hard plaque according to the texture, and can be divided into vulnerable (easy to rupture) plaque and stable plaque according to the stability. Generally speaking, hard plaques are firmly attached to the canal wall and not easily dislodged, while soft plaques are not firmly attached to the wall and easily dislodged. Plaque dislodgement will definitely cause acute occlusion of the cerebral artery of the branch of carotid artery and cause cerebral infarction. If the carotid plaque ruptures, two kinds of hazards will occur: firstly, the material in the ruptured plaque will enter the blood flow and block the distal cerebral artery; secondly, the ruptured plaque will easily cause local trauma thrombosis, and this kind of thrombus attached to the wall will be more easily dislodged, and more seriously, the thrombus will be formed rapidly and grow up quickly to cause acute occlusion of the carotid artery, which is a very serious state. The severity of cerebral infarction depends on the size of the plaque blocking the cerebral artery and the location of the blocked vessel. At present, the timing of plaque dislodgement cannot be accurately measured, and the site of blockage cannot be located, so once a plaque is found in the carotid artery, it should be actively diagnosed and treated.