Abstract: Objective To analyze the components of carotid atherosclerotic plaques with gemstone spectral CT. Methods Forty-three cases with ischemic symptoms who showed carotid atherosclerotic plaques by ultrasound and MRI underwent CTA of carotid artery by gemstone spectral imaging(GSI).Process the hybrid images to the single images,then do the semi-quantitative analysis of energy spectrum material of the plaques to get the slope of curve and effective atomic number of the different tissues with the aid of 3D-reconstruction and GSI viewer.The statistical methods are general statistical description(such as mean and standard deviation). Results Ninety-eight lesions,including 37 lipid plaques (37.76%),48 fibrous plaques (48.98%),and 13 plaque hemorrhage (13.26%).The rules of spectrum curve of each component of the plaque:lipid deposition show an arched upward curve,CT values increase gradually with higher energy.Fibrous matrix and intraplaque hemorrhage reveal the attenuation curve,CT values decrease gradually with higher energy.And the attenuation amplitude of fibrous matrix is higher than that of intraplaque hemorrhage in low energy area.In lower energy area,the dispersion degree of three components is more obvious.The slopes of curve and effective atomic numbers of lipid deposit,fiber content,intraplaque hemorrhage were -3.54±0.78,2.36±0.56,0.45±0.09 and 3.24±0.80,8.56±0.63,7.26±0.59,respectively.There were statistical differences between any two kinds of plaques (all P＜0.05). Conclusion Spectral CT angiography can give more quantifiable data(lipid composition,fiber content,plaque hemorrhage ingredients) of carotid atherosclerotic plaques to help us judging the extent of the atherosclerosis of the vessel.