In this paper, the authors investigated the dynamic process of a high-level paleolandslide blocking river event-Gangda landslide blocking river event in the deep valley area. An integrated fluid-solid coupling method based on the FDEM-SPH was proposed to study it. In the numerical model, the dynamic process of the landslide is described by FDEM, while SPH describes the behavior of the river water. Based on the back-analysis of the three-dimension modeling, the landslide blocking river simulation results of the FDEM-SPH agree well with the field investigation and PFC3D simulation results. Simulation results of the FDEM-SPH show that the primary process of the Gangda paleolandslide blocking river lasted for 60 s. The maximum overall feature speed of the sliding mass was 33 m/s, while the speed of the sliding mass tip reached a maximum value of 40 m/s. Dynamic fragmentation of the landslide was violent, and both the open mode and sliding mode damage play essential roles in dynamic fragmentation. The variation of kinetic energy, accumulated friction dissipation, and fracture energy of the sliding mass are also shown. The landslide induced an impulse wave after merging into the river, and the wave behavior was further affected by the sliding mass movement. The maximum overall feature speed of the wave was 17 m/s, and the speed of the wave tip reached a maximum value of 33 m/s with a maximum run-up height of 120 m. Finally, a comparison of the FDEM-SPH model and PFC model in the application of landslide blocking river is discussed, and the advantages and limitations of the FDEM-SPH model are examined.