Real-time simplification of terrain is very important in visualization of 3D terrain and Virtual Reality(VR). To best exploit the rendering performance

the scene complexity must be reduced as much as possible without leading to an inferior visual representation. The most common way to increase efficiency is the use of different levels of detail(LODs) for different areas of the scene. The algorithm in this paper is a real-time terrain simplification algorithm

based on local entropy. The algorithm adopts quadtree structure

which can provide real-time computation and high efficiency. The algorithm uses "Local Entropy" as error metric

improving the quality of simplified results. In an aspect of fixing "gaps" that is unavoidable in quadtree structure

the algorithm adopts more rational data structure to acquire higher efficiency. The experiment results indicate that the algorithm is practice and effective

which can meet the demand of real-time rendering in 3D terrain simplification and VR.