Abstract: A vertical two dimensional coupling model of air-water-mud system is established to investigate the response of mud-water interface to surface waves, in which the mud is considered as a Newtonian fluid with high viscosity and turbulence is modeled by means of the SST (shear-stress transport). The VOF(volume of fluid) method is adopted to capture free surface, as well as mud-water interface. Different computational cases are considered according to five amplitudes and four periods of the surface wave to delineate the dependence of mud layer motion on the nonlinearity and the dispersivity of surface waves. The numerical results suggest that the mud-water interface undulates with the same wave length and period as the surface wave, albeit with a phase lead, which seems independent of the surface wave height and period. The wave height of the mud-water interface is almost proportional to that of the surface wave, and tends to increase with the period.