Objective To investigate cerebral autoregulation(CA)in patients with severe unilateral carotid artery stenosis by near infrared spectroscopy. Methods Thirty patients who underwent general anesthesia in our hospital from January 2015 to February 2017 were enrolled in this study.The stenosis group included 15 patients with severe unilateral internal carotid artery stenosis,and the control group included 15 patients without carotid artery stenosis.Both groups were matched in sex and age.Cerebral tissue oxygenation index(TOI)and mean arterial pressure were recorded continuously under stable general anesthesia.The Pearson correlation coefficient(r)was calculated to judge the CA status. Results TOI was not significantly different between the stenosis side and the non-stenosis side in the stenosis group(66.52±6.50 vs. 65.23±4.50;t=0.93, P=0.368)or between the stenosis side in the stenosis group and the stenosis side in the control group(66.52±6.50 vs. 64.22±3.87;t=1.18, P=0.248).The r values of stenosis side and non-stenosis side in the stenosis group were 0.36±0.12 and 0.17±0.11,respectively,and the r values of the stenosis side in the stenosis group and the stenosis side of the control group were 0.36±0.12 and 0.13±0.08,respectively.In the stenosis group,5 patients had transient ischemic attack and 2 patients had a history of stroke within 3 months before operation.When an r value of 0.342 was used as the judgment point of CA abnormality,the sensitivity and specificity were 0.625 and 0.909,respectively. Conclusion Within the range of normal blood pressure fluctuation,cerebral blood flow is linked to blood pressure at the stenosis side in patients with severe unilateral carotid artery stenosis.