Objective To compare the effects of different contrast media injection plan on the quality of images of 64 slice spiral CT angiography (CTA) in the same iodine concentration. Methods 100 patients with suspected cerebral aneurysms were randomly divided into two groups. Group A were injected with 70ml contrast agent at the rate of 3.5ml/s. Group B were injected with 50ml at the first stage and the rate was 3.5ml/s. Remaiding contrast agent were injected with 20ml at the second stage and the rate was 2.0ml/s. To measure the CT value of the right carotid artery in the carotid artery bifurcation level, basilar artery, right middle cerebral artery and torcula by analyze the transversal images and MPR images. To observe the cerebral artery branches display at the same time. Results The CT value of torcula in group A were significantly higher than that in group B (P<0.05) and there were statistically significant difference between the two groups.There were no significantly difference in CT value of the arteries between the two groups (P>0.05). Conclusion The venous interference by dual phase injection of iodine contrast agent in cerebral CTA was significantly lower than single phase injection.The image quality was better at the same time.