Abstract: Multilayer film-substrate structures have been widely used in the industrial field, in which the thickness and elastic parameters of thin films have significant effects on the structure and device performance. However, it is difficult to determine the material parameters of multilayer films in nondestructive testing. Considering that the interface wave is sensitive to the materials near the interface and that the Scholte wave dispersion caused by layered films is closely related to the velocity distribution of layered materials, in this paper, the sound propagation in the layered structure is analyzed by using the global matrix theory and the expression of the sound pressure with impulse excitation on the interface is given. On this basis, the Scholte wave dispersion curves at the liquid-solid interfaces in the water-immersed bilayer film-substrate structures with the sound speeds showing positive gradient, negative gradient and random distributions are numerically calculated. Furthermore, the variation of the transient interface wave signal excited by the normal pulse line source with the thickness of the film is calculated in detail. The results show that the thickness of two films has a significant effect on the dispersion characteristics of liquid-solid interface, and the "trapping" effects (frequency selectivity) of Scholte waves in different frequency bands are obvious for different film thicknesses. The results provide a theoretical basis for further thickness determination of multilayer films based on Scholte wave dispersion characteristics.