In order to investigate the dynamic response of hard crust under the low embankment of soft subsoil, the road system on soft subsoil is simulated into pavement – subgrade – hard crust – soft subsoil layers of structure. The pavement, subgrade and hard crust are regarded as three elastic layers resting on a poroelastic porous medium simulation. Solution is derived by using the integral transform model, the dynamic stiffness matrix for the pavement; subgrade, hard crust and soft subsoil are set up respectively. The dynamic response equations for the layer which considered the effect of vehicle load are obtained by integrating the overall dynamic stiffness matrix of structure. On this basis, numerical results are derived through the inverse fast Fourier transform (FFT) method and used to analyze the influences of thickness, modulus and Poisson ratio of hard crust on stress dispersion. It is shown that the existence of the hard crust weakened the vertical dynamic stress of soft foundation greatly and increased the range of diffusion. And the responses of soft subsoil are very sensitive to the change of thickness and modulus. Therefore, it can be concluded that the dynamic response of traffic load is significantly diffused by hard crust.