Abstract: Modeling of post-failure flow of landslides is one of the important approaches that can be used to simulate landslide flow development and predict the landslide hazard zone. A Smoothed particle hydrodynamics (SPH) model based on the constitution of elastic-plastic constitutive mechanics for soil is developed for simulating the behavior of a class of geo-materials. The SPH soil model considers the plastic behavior of the materials, and hence it is very important for more accurate and realistic simulations of geo-materials of soil type. The implemented material laws in the SPH soil code include classical elastic-plasticity with a linear elastic part, and different applicable yield surfaces with non-associated flow rules. In order to apply the SPH method to actual landslide modeling, the geographic information system (GIS) is utilized to generate site-specific models. Thus a C# code is developed to generate the particles of a given landslide site, which produces realistic particle mass and actual complicated boundaries for the SPH soil model. With GIS enabled, complex topography and irregular boundary can be accurately and easily generated. To improve the accuracy of such a complicated landslide simulation, a modified approach is proposed to implement the complex topography representation of landslide mass and the effective treatments of the irregular and complicated boundaries generated from the GIS. The SPH soil code is applied to the well-known Daguangbao landslide triggered by Wenchuan Earthquake in 2008. The topographies after failure are compared with those obtained from field collected data, and good agreement is found.