The normal value of the common carotid artery resistance index is between 0.55 and 0.75. In general, the normal range may vary slightly from hospital to hospital with different instruments. It is generally recognized that if the common carotid artery resistance index exceeds 0.75 or so, it is considered to be abnormal and may have some clinical significance. The common carotid artery resistance index is clinically determined by carotid vascular ultrasound, to determine whether the carotid artery obstruction, if the results of the common carotid artery resistance index is greater than 0.75, the consideration of the vascular lumen may be blocked, so this value reflects the vascular resistance index. If the result is abnormal, we should consult the neurology department regularly, and the professional doctor will judge the condition, and if necessary, carry out the vascular CTA examination to further clarify whether there is stenosis in the carotid blood vessels, and the blood flow resistance is abnormal, so as to further systematic treatment.