The expression of virtual geographic environment is based on the surface modeling, such as three-dimensional terrain modeling and rendering most of which are based on the polygon grid and 2D textured. In the expression of extreme terrain, such as caves, cliffs, canyons it seems powerless. However, the voxel-based terrain modeling has been more useful than polygon modeling expression in the field of real-time terrain deformation, extreme terrain simulation and geographic process expression. Furthermore, virtual geographic environment based on the traditional surface model is difficult to realistically simulate the real world which is volumetric. This paper analyzes the trends of the geographical environment representation, and discusses the typical voxel-based applications in natural phenomena simulation, terrain modeling and spatial process analysis. It provides the references for the integrative representation of the unified voxel and surface model, and for the construction of virtual geographic environment unified platform.