Objective To investigate the correlation between the DWI-FLAIR mismatch and collateral circulation. Methods AIS patients were recruited prospectively to undergo multimodal MR within 24 hours after onset.Some cases also underwent angiography. DWI-FLAIR mismatch is defined as DWI-positive and FLAIR-negative, DWI-FLAIR match as both positive.FLAIR hyperintense vessles signs (FHV) is described as focal, tubular, or serpentine hyperintensities in the distal of large arteries in the subarachnoid space.Collateral perfusion was graded by the American Society of Interventional and Therapeutic Neuroradiology criteria, 0~2 was graded as poor,3~4 was graded as good. Results 43 patients were included.17 patients also underwent angiography.DWI was 100% positive,FLAIR was 30.2% positive. FHV identified patients with proximal large artery occlusion or severe stenosis with 62%(95% CI 41%~79%)sensitivity，88%(62%~98%) specificity,89%(64%~98%)positive predictive value，60%(39%~78%)negative predictive value.There was no significant difference of FHV presence (p=0.925) and collateral perfusion grade (Fisher's exact test p=0.644) between the two groups. Conclusions FHV can help to identify proximal large artery occlusion or severe stenosis in AIS.DWI-FLAIR mismatch is insufficient to predict collateral circulation