Objective To compare the difference of automatic boneless and subtraction boneless technologyin cerebral vascular image of 256-slice spiral CT image quality. Methods Retrospective analysis cerebrovascular disease(such as calcification, aneurysm) clinical data of 47 patients. According to the different way of post-processing method, all cerebral images divided into control group and observationgroup.control group underwent automatic boneless technology, the observation group received subtraction boneless technology, difference comparison of image quality between two groups of cerebral angiography. To compare the successive rates of the two methods. Two observers of the subjective image quality score using Kappa consistency test, image subjective ratings Comparison between two groups was done with independent sample T-test. Results The control group and observation group boneless success rate was 70.21% (33/47) and 93.62% (44/47). The correlation coefficient of two observers was 0.914，Image quality of observation group was significantly higher than the control group in the image, the image quality was statistically difference between the two groups (2.76±0.84) vs (3.68±0.73), t=5.978, P<0.05). Conclusion In intracranial vascular siphon segment with calcification, subtraction boneless technology can significantly improve the accuracy of diagnosis, the clinical suspicion small aneurysms or assess artery stenosis degree, boneless technology, adopt subtraction angiography can reduce missed diagnosis and reduce the narrow exaggerated effect. Clinically suspected small aneurysms subtraction boneless technology can reduce missed diagnosis and reduce the narrow exaggerated effect.