Objective To explore the value of non-contrast CT (NCCT), CT perfusion imaging (CTP) and CT angiography (CTA) in the diagnosis of cerebral collateral circulation of ischemic stroke. Methods A total of 47 patients with ischemic stroke were selected and examined with multi-mode CT (NCCT, CTP, CTA) within 3d after admission. The cerebral blood flow (CBF), cerebral blood volume (VBV), mean transit time (MTT), time to peak (TTP) and CTP were recorded. All patients were followed up for 90d, and the modified Rankin scale (mRS) scores were recorded. Related statistical analysis was performed. Results In the 47 patients, the multi-mode CT examination showed that there were 18 cases without vascular abnormalities and 29 cases with vascular stenosis or occlusion. In the 29 cases with vascular stenosis or occlusion, there were 13 cases with good collateral circulation (good collateral circulation group) and 16 cases with poor collateral circulation (poor collateral circulation group). The CBF of the affected side was significantly lower than that of the contralateral side in the good collateral circulation group (P<0.05), and MTT and TTP were significantly longer than those of the contralateral side (P<0.05), without significant difference in CBV between the two sides (P>0.05). 90d of follow-up showed that the prognosis of patients in good collateral circulation group was good. In the poor collateral circulation group, the CBV and CBF of the affected side were significantly lower than those of the contralateral side (P<0.05), and the MTT and TTP were significantly longer than those of the contralateral side (P<0.05). 90d of follow-up showed that the prognosis of patients in poor collateral circulation group was poor. Conclusion The combined examination of NCCT, CTP and CTA is of great value in evaluating cerebral collateral circulation and the prognosis of ischemic stroke.