Abstract: The dynamic shear modulus and damping ratio are essential parameters for the site seismic response analysis of major projects. During highway construction along the Yellow River, the feasibility of using Yellow River sediment as a subgrade filler has been verified and valued. However, the dynamic characteristics of Yellow River sediment as subgrade filler are rarely studied. In this paper, the British GDS dynamic triaxial test system was used to perform dynamic triaxial stress control tests on the sediment taken from the Zhengzhou section of the middle and lower reaches of the Yellow River. A total of 11 groups of tests were performed to explore the effects of confining pressure, relative density, and test frequency on the dynamic shear stress–dynamic shear strain relationship, dynamic shear modulus G, and damping ratio D of Yellow River sediment. The backbone curve and hysteresis curve of the dynamic shear stress–dynamic shear strain relationship were plotted. The results show that the relationship between the dynamic shear modulus, damping ratio, and shear strain of Yellow River sediment can be described by the Hardin hyperbolic model, and confining pressure has the greatest influence on the dynamic shear modulus and damping ratio of Yellow River sediment. For a given shear strain condition, the larger the confining pressure is, the larger the dynamic shear modulus. When the strain level is large, the dynamic shear modulus increases with the relative density; the damping ratio decreases with increasing confining pressure and increasing relative density. Frequency has no obvious effect on the dynamic shear modulus and damping ratio. A comprehensive comparison with the dynamic characteristics of other soils shows that the dynamic shear modulus reduction curve law and damping ratio D curve law of Yellow River sediment are consistent with those of other soils, and their dynamic characteristics are closer to silt and sand, but not completely consistent with those of other soils, with certain particularity. Finally, considering the influence of confining pressure and relative density, combined with the existing empirical formula, an empirical formula that can better describe the relationship between the maximum dynamic shear modulus G_max and the confining pressure and void ratio of Yellow River sediment is established. Additionally, a mathematical model of the dynamic shear modulus ratio G/G_max and D is established. The fitting results show that the established model can better describe the variation in G/G_max and D with the shear strain of Yellow River sediment. This capability provides an important basis for the seismic design of Yellow River sediment as subgrade filler.