Abstract: Objective: To investigate the value of conventional CT angiography(CTA) and subtraction CTA(SCTA) on the discrimination of degree and diagnosis of carotid artery stenosis. Methods: The conventional CTA, subtraction CTA and digital subtraction angiography(DSA) were used to perform carotid arteriography in 45 cases of suspected patients with carotid artery stenosis. The evaluation method of diagnostic assay was used to compare the concordance rate of the degree of carotid stenosis between the two CTAs and DSA, and their diagnostic value on carotid artery stenosis. Results: Conventional CTA showed 62 carotid stenosis, 80 by SCTA and 76 by DSA. There had no differences between SCTA and DSA detection of carotid stenosis(P<0.05). The sensitivity, specificity, positive predictive value and negative predictive value of conventional CTA in diagnosis of carotid artery stenosis were 78.9%(60/76), 85.7%(12/14), 96.8%(60/62) and 42.9%(6/14), respectively. The sensitivity, specificity, positive predictive value and negative predictive value of SCTA in diagnosis of carotid artery stenosis were 98.7%(75/76), 64.3%(9/14), 93.7%(75/80) and 90.0%(9/10). Compared with the conventional CTA, the sensitivity in SCTA was higher(P<0.05). Conclusions: SCTA has a better ability on discrimination of degree of carotid artery stenosis than the conventional CTA.