Abstract: Digital elevation data is widely used in all kinds of fields and it is a common data source for terrain analysis and other spatial applications. Methods of displaying digital fields based on DEM data are discussed. Data format of DEM data is given, together with the method of effectively reading DEM data. A method of terrain display using OpenGL graphical interface is put forwarded. In the meantime, some key points related to the display of 3D terrain are described and an instance using OpenGL is given. Some methods of simplification that can be used for further work are also given.