Objective To study the value of whole brain CT perfusion imaging (CTP) combined with head and neck CT angiography (CTA) in the diagnosis of acute ischemic stroke (AIS). Methods A total of 294 cases of patients with suspected AIS in our hospital were given CT plain scan, CTP and CTA respectively. The sensitivity and specificity of CTP combined with CTA was analyzed. The CTP parameters of CBF, CBV, MMT and TTP were measured, and the degree of cerebral artery stenosis was evaluated. And the changes of CBF, CBV, MMT and TTP in brain tissue of different lesions and their correlation with the degree of cerebral artery stenosis were analyzed. Results Of 294 patients, 253 cases (86.05%) were diagnosed as AIS. The sensitivity and specificity of CTP combined with CTA were 85.37% and 92.68% respectively. The CTP examination revealed 207 cases of obviously abnormal perfusion, including 194 infarcts, 182 penumbra and 173 of existence simultaneously, and the CBF and CBV in infarct area were lower than those in control area and penumbra while the MTT and TTP were higher than those in control area and penumbra (P<0.05). The CBF in penumbra was lower than that in control area while the MTT and TTP were higher than those in control area (P<0.05). Pearson correlation coefficient analysis showed the degree of internal carotid artery and intracranial artery stenosis was not significantly correlated with CBF and CBV (P>0.05), and negatively correlated with MTT (P<0.05), and positively correlated with TTP (P<0.05), but the correlation degree was low. Conclusion CTP can effectively assess the hemodynamic changes and ischemic severity of brain tissue, and distinguish the infarct zone and penumbra accurately. CTA can accurately detect the location and degree of cerebral artery stenosis. The combination of the two methods can not only be used for accurate diagnosis of AIS, but also for assessment of condition changes, so as to provide images support for clinically treatment regimens selection.