Objective To investigate the application value of 3D arterial spin labeling (ASL) perfusion imaging for patients with unilateral carotid stenosis or occlusion.Methods Cervical MRA and cerebral 3D ASL were performed on 36 consecutive patients with unilateral carotid stenosis diagnosed by digital subtraction angiography (DSA).The consistency of degree of stenosis between cervical MRA and DSA was analyzed.36 patients were divided into mild,moderate and severe groups by degree of stenosis,which was based on the DSA result.Variance analysis of cerebral blood flow (CBF) unilateral and contralateral changes were performed on three different groups.Patients with severe stenosis,diagnosed by DSA,were divided into symptomatic group and asymptomatic group.Analysis was carried out on unilateral and contralateral change differences between symptomatic group and asymptomatic group.Results There was no statistical significance between MRA and DSA in the cervical artery stenosis degree (kappa＞ 0.75,P＜0.05).There was no statistical difference in CBF unilateral and contralateral changes between mild group and moderate group (P＞0.01).There was statistical difference in CBF unilateral and contralateral changes between severe group and other two groups (P＜0.01).There was statistical difference in CBF unilateral and contralateral changes between symptomatic group and asymptomatic group (P＜0.01).Conclusion 3D ASL as a safe,non-invasive,repeatable method,are meaningful for cerebral hemodynamics evaluation in patients with unilateral carotid stenosis.