Generating and propagation of a landslide-induced tsunami is clarified by carrying out the hydraulic and numerical experiments in the open-channel. The effect of the interactive force between layers of the debris flow and the water is important to generate a tsunami, controlling the amplitude and wave period. The numerical simulation using the model of two-layer with shear stress models on the bottom and interface is applied to the present experiments and is compared with its results. Selecting the appropriate coefficients of them, calculated the debris flow agrees with the measured results, and ensures the process of rushing into the water. And the wave frequency dispersion effect in upper-layer is essential to simulate the propagation and discuss the numerical methods to introduce the effect. The method of the mixed explicit and implicit schemes in two steps enables to simulate the tsunami propagation as long as the initial profile of tsunami is given as boundary.