Objective To discuss the role in perfusion weighted imaging(PWI) evaluation of collateral circulation for patients with posterior circulation ischemia(PCI) induced by vertebral basilar artery stenosis. Methods 76 cases of patients with PCI induced by vertebral basilar artery stenosis treated from our hospital during the period of January 2014 and January 2017 were selected as case group, 75 cases of health physical examination without vertebral basilar artery stenosis were selected as control group, all study object were given PWI examination. Results PWI examination of the case group showed low perfusion change, and two-side cerebral anterior, middle and posterior arterial and internal carotid artery showed good results, vascular cavity was smooth and the vessel wall was smooth， intact. The proportion of microarterial shown, pial artery shown, posterior communicating artery patency of the case group were significantly higher than that in the control group, and the difference between the two groups was statistically significant (P<0.05). Compared with the control group, rMTT of the case group was significantly prolonged, rCBV and rCBF were significantly reduced, and the difference between the two groups was statistically significant (P<0.05). The coincidence rate of vertebral basilar artery stenosis between PWI and DSA examination was 94.74%. Conclusion PWI can accurately evaluate the compensatory function of collateral circulation for patients with PCIinduced by vertebral basilar artery stenosis, understand the status of ischemic tissues hemodynamics, offer significant guidance for treatment plan and prognosis evaluation, it is worthy of clinical popularization and application.