The modeling of the influence scope after slope failure is one of the important approaches to quantify the risk of landslide hazard. In this paper, based on the Smoothed Particle Hydrodynamics (SPH) method, the classical elastoplastic constitutive model was employed to study the application of a more accurate and convenient method to simulate the influence scope of slope failure with a series of numerical treatments. Geographic Information System (GIS) platform and C# programming were adopted to build the model of the terrain details and features of the slope using SPH particles. At the same time the arrangement of boundary particles in the model were improved. Finally, a program that can automatically generate the data of landslide particles for calculation and simulation was completed. The model and method were applied to the Oso landslide case in Washington state, USA and the simulation results were basically consistent with the data collected from the field.It is verified that the SPH method and the model can be used to simulate the process and influence scope of slope failure.