The application of Smoothed Particle Hydrodynamics (SPH) method to the simulation of granular materials under large deformation is presented. The Drucker-Prager constitutive model with non-associated flow rule is implemented into the SPH formulations to model the granular flow in a continuum framework. Simulations of the collapse of 3-D axisymmetric sand columns with various aspect ratios are conducted to validate the developed model. Numerical results of the granular flow pattern and final runout distance are in good agreement with the experimental observations as reported in literature. This study indicates that despite being a continuum-scale model, the developed SPH model can be used to effectively simulate large deformation and dense flow of granular materials, and geomaterials in general if proper constitutive models are implemented. Therefore, the developed model may find applications in various problems involving dense granular flow such as landslides and debris flow.