Cerebral hyperperfusion syndrome (CHS) is one of the severe complication after carotid artery stenting with a high mortality rate. CHS was defined as cerebral hyperperfusion (CH) with clinical symptoms such as unilateral headache, convulsions, hemiparesis/hemiplegia, visual disturbances, ataxia, aphasia, while CH could be a disastrous outcome causing complication after carotid revascularization if not managed properly and timely. This is a single-center prospective cohort study to investigate the risks of CH after carotid artery stenting. All patients with severe carotid artery stenosis underwent carotid arterial ultrasonography and dynamic cerebral autoregulation (dCA) test by transcranial Doppler sonography (TCD) before operation. The postoperative carotid ultrasound and transcranial Doppler sonography (TCD) results are also needed. The investigators will collect this test data at 48h, 1 month and 3months after carotid artery stenting（CAS）. According to the examination results, they were divided into two groups: CH group and non-CH group. The investigators will collect data before CAS, on all participants' age, sex, heart rate, BP and end-tidal carbon dioxide (ET-CO2) and the following information from the patients : (i)demographic data, such as hypertension, coronary heart disease, diabetes, hyperlipidemia, smoking and body mass index; (ii) relevant clinical symptoms; (iii) preoperative colour Doppler ultrasonography（CDU）and transcranial Doppler sonography(TCD) results; (iv) The cerebral blood flow velocity (CBFV) of the middle cerebral artery（MCA） induced will be measured by non-invasively and continuously dCA test. This study could be aimed to analyze the factors influencing cerebral hyperperfusion after CAS. The purpose of this study will be to perform more precise risk stratification for high-risk CH patients and improve the quality of life of them. Statistical Analysis The Statistical Package for the Social Sciences（SPSS）software Version 26.0 (IBM, New York, USA) will be used for statistical analyses. The indicators with P < 0.2 in the univariate analysis will be entered into a logistic regression analysis to investigate the independent risk factors for CH after CAS. All tests will be performed two sided, and a P < 0.05 will be considered statistically significant.