Abstract: Objective. To study the changes of delayed scan after CT perfusion imaging in the right middle cerebral artery occlusion of rats,combining with histologic outcomes(light and electron microscopy).To investigation of blood-brain barrier damage after acute ischemic stroke.Methods. All 25 rats were divided into 5 groups.And the MCAO(middle cerebral artery occlusion) model were set up.Every groups performed routine scan,CT perfusion imaging(CTPI),and delayed scan in turn.All rats were killed immediately after scan and dealt with light and electron microscopy.Results. In group A,no abnormal outcomes were found in delayed scan.In group E,enhancement in the ipsilateral cortex in delayed scan were seen.And in light and electron microscopy most neurons were markedly shrunken,some of them had pyknotic nuclei and eosinophilic cytoplasm.Conclusion. Delayed scan can evaluate blood-brain barrier damage of acute ischemic stroke.