Atherosclerosis is a general term for pathological changes such as thickening, hardening and loss of elasticity of arterial walls, which can involve large, medium and small arteries. Early atherosclerotic hemodynamics do not change significantly. When the lumen is severely narrowed, the blood flow is accelerated; if the narrowed segment is long, the blood flow is slow. Atherosclerosis is manifested in two-dimensional ultrasound as intimal thickening and convexity into the vessel lumen. Atherosclerotic plaque formation is considered when the carotid intima-media thickness is greater than 1.0 mm. Plaque echogenicity can be divided into hypoechoic (soft plaque), moderate and hyperechoic (hard plaque) and inhomogeneous echogenicity (mixed plaque). Color multispectral can show colored flow filling defects at the plaque and bright or multicolored mosaic flow signals in the lumen; when the stenotic segment is long, color multispectral shows tiny flow bundles at the stenosis; when the artery is occluded, no flow signal is shown or reverse flow is seen proximal to the occlusion. Spectral multispectral flow parameters used to evaluate the degree of arterial stenosis include peak systolic flow velocity, diastolic flow velocity or flow ratio, and spectral patterns (band broadening) can also be used to infer the degree of stenosis. A variety of evaluation indicators are used to evaluate the degree of stenosis in atherosclerosis.