Abstract: A gas-liquid interface and its changes in position have impacts on the propagation and amplitude of pseudoRayleigh waves at the fluid-solid interface, which is studied in this paper. A numerical simulation (finite-difference method) is performed to model the surface wave of different gas-liquid interface position generated by a near-surface impulsive plane source in the solid with vibration direction perpendicular to the fluid-solid interface, through which the influence of scattering brought by the gas-liquid interface itself and the energy leak in the propagation process is discussed. The simulation result shows that, the influence of the scattering effect of gas-liquid interface itself very slightly contributes to the amplitude of pseudo-Rayleigh waves, and the predominant cause of attenuation is the energy leak; with the gas-liquid interface position increases, the amplitude of pseudo-Rayleigh wave pulse declines exponentially and its central frequency becomes lower. This result can be developed into a method for liquid level detection using the amplitude of pseudo-Rayleigh waves.