3D (three-dimensional) process simulation is currently one of the most challenging fields of research on debris flow. Large scale terrain rendering is the most basic task of 3D scenery construction in debris flow simulation. As the major trigger for debris flow, rainfall will substantially enhance the realistic sense. Terrain and rainfall rendering in 3D debris flow simulations poses great challenges for numerical computation and graphical processing capability. In this paper, we propose to integrate GPU technology, LoD algorithms, and particle systems to realize 3D scenery modeling and rendering. The real-time LoD-based terrainmodeling and rendering algorithm is presented first, and then a particle system-based rainfall scenery rendering method is implemented. Experimental results demonstrate that the 3D scenery rendered with the proposed approach exhibits sound performance and fair visual effects, which lays a solid foundation for the whole process simulation of debris flow disasters.