Abstract: By using the GDS-RCA resonant column system, the dynamic characteristics of rubber-sand mixtures (RSMs) under different rubber contents, particle size ratios and confining pressures are tested, and the coupling effect law and mechanism of three factors on the dynamic characteristics of RSM are explored. First of all, the dynamic shear modulus and damping ratio curves of RSMs with four types of rubber contents and particle size ratios under three confining pressures are obtained through experiments. Then, the influences of particle size ratio on the dynamic shear modulus, the maximum dynamic shear modulus, the reference shear strain and the damping ratio curve of RSMs are discussed, and the coupling effects of particle size ratio, rubber content and confining pressure on the dynamic characteristics of RSMs are also analyzed. Finally, the phenomenon and conclusion are further verified by comparing with the existing literatures. The results show that the particle size ratio has a significant effect on the dynamic characteristics of RSMs, and the maximum dynamic shear modulus changes even 3 to 4 times when it changes. There is a coupling effect between the particle size ratio and the rubber content on the dynamic characteristics of RSMs. The effects of the particle size ratio under low rubber content are significantly different from those under high rubber content, but the influences of confining pressure and particle size ratio on the dynamic characteristics of RSMs have no obvious coupling effect. The maximum shear modulus of RSMs can be estimated by treating the volume of rubber as voids with the empirical equations proposed by Hardin et al.