The dynamic characteristics of rockfill materials are very important to the seismic design of earth-rock dams.However，most of the current research is based on uniaxial cyclic vibration triaxial tests，neglecting the impact of radial vibration on the soil. It is significantly different from actual seismic effects. The variation laws of dynamic modulus and damping ratio of rockfill materials under bidirectional vibration were investigated through laboratory experiments. The differences in dynamic characteristics of rockfill materials were revealed under uniaxial and bidirectional vibration. The results indicate that the variations of dynamic modulus and damping ratio on the rockfill material under single and bidirectional vibration are consistent. As the confining pressure increases，the dynamic modulus increases and the damping ratio decreases. Under the same conditions，the dynamic modulus of bidirectional vibration is smaller and the damping ratio is slightly larger. The initial vibration has a significant impact on the dynamic modulus，and a slight effect on the damping ratio. The research results can provide a reference for the design of earth rock dams filling materials.