Clay-rock mixtures are widely used as subgrade filler in projects, but there are few studies about their dynamic response under the influence of traffic loading. For this reason, according to different gravel contents and confining pressures, the dynamic shear modulus and damping ratio of the clay-rock mixture at small strain (10^-6-10^-4) were studied with the free vibration column instrument. In this paper, the soil/rock threshold was set as 0.05 L_c(L_c is diameter of the traxial sample). Results showed that the maximum dynamic shear modulus increases with increasing gravel content in the mixture, has a greater increase in amplitude when the content of the gravel is 20%-40%, and increases with increasing confining pressure. Under the same strain amplitude, the decay in dynamic shear modulus decreases with increasing gravel content, decreases greatly in the content range of 20%-40%, and decreases with increasing confining pressure. Minimum and maximum damping ratios both decrease with increasing gravel content and confining pressure. Based on the test results, the influence mechanism of gravel content and confining pressure on the dynamic shear modulus and damping ratio of the clay-rock mixture is put forward. Finally, the estimation formula among gravel content, confining pressure, and dynamic behavior parameters of the clay-rock mixture are established with the modified Hardin-Drnevich model, with the aim of providing theoretical guidance for the design and construction of soil-rock mixed subgrade.