The landslide generated tsunami is one of the most devastating nature hazards. However, the involvement of the moving obstacle and dynamic free-surface movement makes the numerical simulation a difficult task. In this study, a two-way coupled moving solid algorithm was developed. We solved the 3D large eddy simulation (LES) turbulence model for the fluid part. The obstacle was moving on a fixed grid. The pushing effect of the moving obstacle on the fluid was introduced by specifying the boundary velocities on the cell faces where obstacle was located. The partial cell treatment was adopted for the grids partially occupied by the solid material. To predict the solid movement, the stress on the solid material was integrated and coupled with the sophisticated discrete element method (DEM) model. After validation, this model then was applied to studying the landslide generated tsunami, and the yielded results were compared with a series of experiments of landslide tsunamis. Good agreement and discussion were presented.