Objective To investigate the 128 slice spiral CT cerebral perfusion imaging and half low dose scan time of the feasibility and value. Methods The patients whom were suspected of ischemic cerebrovascular disease or symptoms due to vertigo were randomly divided into 2 groups by using the random number table. The 20 phase of continuous dynamic scanning were performed in group A, with total scanning time 30s, and produced a total of the 20 volume data group. The 40 phase of continuous dynamic scanning were performed in group B, with total scanning time 60s, and produced a total of the 40 volume data group. Observe 2 groups of radiation dose and perfusion index. Results The volume dose index, dose rate product and effective dose of group A were significantly lower than those of group B(P<0.05) . There was no significant difference in the levels of CBF, CBV and MTT in the caudate nucleus, frontal lobe white matter and temporal occipital white matter between the 2 groups(P>0.05). The 2 groups of pseudo color images are all clear, which can meet the needs of diagnosis. Conclusion The 128 slice spiral CT half time low dose scan can reduce the radiation dose of the brain significantly, and obtain ideal perfusion parameters, which was worthy of further study.