A simplified model algorithm based on vertex normal vector is presented aiming for real-time rendering of large-scale three-dimensional terrain problem. In the rendering process，blocks are cut quickly by the projection of body views; the data blocks which are apart from body views are discarded; and the partially visible or fully visible blocks are loaded into the memory. This algorithm constructs node resolution evaluation function according to the distance(between the viewpoint and the node) and the roughness of the terrain as well. It eliminates cracks by adding points. Simulation results show that the proposed algorithm can reduce the number of triangles and the time required to render the terrain effectively.