Objective To analyze the effects of 64 slice spiral CT reconstruction techniques (VR, MIP) and Doppler ultrasound in the diagnosis of the degree of internal carotid artery stenosis. Methods Seventy-two patients with ischemic cerebrovascular diseases and clinically highly suspected internal carotid artery stenosis who were treated in our hospital between March 2014 and March 2016 were selected as study subjects. CT angiography (CTA) and Doppler ultrasound were performed at the same time within 7 days. The image reconstruction methods of CTA included maximum intensity projection (MIP) and volume rendering (VR), and digital subtraction angiography (DSA) was taken as the gold standard control. Results Among 72 patients, there were 44 patients (walls of 62 internal carotid arteries) with different degrees of calcification, and both of MIP and VR examination can show the site and shape of calcification. Compared with axial images, MIP images showed that calcification in walls of 3 carotid arteries was not displayed (P >0.05) while VR images showed 13 such carotid arteries (P<0.05). In 281 segments of 72 patients, 209 segments were confirmed by DSA, showing different degrees of vascular stenosis. There were mild, moderate and severe stenosis in 61 segment, 56 segments and 49 segments respectively, and 43 segments were with total occlusion. The accuracy rates of CTA in the diagnosis of mild, moderate and severe stenosis and total occlusion (100%, 96.42%, 96.08%, 100%) were slightly higher than those of Doppler ultrasound (96.83, 98.21%, 94.23%, 90.70%) (P>0.05). Conclusion The accuracy rates of 64 slice spiral CT reconstruction techniques are slightly higher than Doppler ultrasound in the diagnosis of the degree of internal carotid artery stenosis. It also can well display angiosteosis. The two can diagnose the degree of internal carotid artery stenosis by combining color of blood flow and diameter of blood flow stenosis.