Debris flows caused by heavy rainfall occur along long watersheds and travel at extremely rapid velocities. Such debris flows can impact large areas and often cause economic and social damages. In order to prevent the damages, barriers against debris flows have been constructed. However, the effect of barriers on debris flow behavior are not fully understood. This paper presents the results of velocity and volume of debris flows according to installation of barriers using DAN3D based on SPH (Smoothed Particle Hydrodynamics) method. These results will be used for application of barriers.