As a common road subgrade fill in Northwest China, the dynamic properties of remoulded loess are the key to study the structural stability of loess subgrade, which is of great practical significance to the engineering construction and operation safety of roads in the corresponding region. This paper takes the remoulded loess of a roadbed in Shaanxi as the research object, and through the indoor dynamic triaxial test simulating traffic cyclic loading, the dynamic shear stress–shear strain relationship, dynamic shear modulus and damping ratio, and other dynamic characteristics of the soil under different water content, dry density and peripheral pressure are investigated and combined with the SEM test to qualitatively and quantitatively analyse the microstructural characteristics of the soil after vibration, so that the changes in dynamic characteristics of remoulded loess are caused by the microcosmic point of view. The results show that the dynamic shear stress–shear strain curve of the remoulded loess shows a hyperbolic development with an increase first and then a steady development, the dynamic shear modulus shows a sharp decrease at the beginning and a stable trend at the end with the shear strain, the increase of water content will lead to a decreasing trend of both, and the increase of dry density and peripheral pressure will lead to a corresponding increase of both. The test measured that the damping ratio changes in the range of 0.08–0.31 interval, showing a large increase in the initial period, the later interval fluctuation trend; the microstructure of the soil after vibration is studied, comparing the microscopic images and quantitative parameters under different test conditions, explaining the reasons for the change of the dynamics of remoulded loess through the change rule of the pore morphology and distribution, and providing the basis for the actual engineering.