Objective To study the cognitive function and characteristics of infarct-free severe carotid artery stenosis （CAS） patients with vascular cognitive impairment （VCI）， and to analyze the risk factors for VCI in these patients. Methods A total of 55 severe CAS patients who were treated in Beijing Tiantan Hospital Affiliated to Capital Medical University from September 2020 to December 2021 were included. The patients were assessed by 2019 Chinese Guidelines for Diagnosis and Treatment of VCI. The cognitive function of patients with or without VCI was compared using the Trail Making Test-A （TMT-A）， Trail Making Test-B （TMT-B）， Boston Naming Test Version 2 （BNT-2）， Chinese version of Hopkins Verbal Learning Test （HVLT）， Clock Drawing Test （CDT） and Montreal Cognitive Assessment Scale （MoCA）. The influencing factors of VCI in patients with severe CAS without cerebral infarction were analyzed by multivariate Logistic regression analysis. Results Among 55 patients with severe CAS without cerebral infarction， 40 patients （72.7%） were complicated with VCI. 67.6% （27/40） of patients with VCI had more the 3 dimensions of cognitive impairment. The results of univariate analysis showed that there was significant difference in the age ［（64.00±6.61） years old vs （58.13±6.66） years old］， years of education ［9 （9，12） years vs 12 （12，16） years］ and vertebral artery stenosis ［65.0% （26/40） vs 5/15］ of patients with or without VCI （P＜ 0.05）. When multifactor correction was applied， advanced age （OR=1.165， 95%CI=1.019-1.332） was a risk factor for VCI in patients with carotid stenosis， while higher education （OR=0.681，95%CI=0.490-0.947） and effective Willis loop compensation （OR=5.531， 95%CI=1.027-29.797）were then protective factors. Conclusions Severe CAS patients with VCI have extensive cognitive function impairment， higher education and effective Willis loop compensation are protective factors for cognitive function， and advanced age is a risk factor for cognitive impairment.