As entering the market, Light Detection And Ranging (LiDAR) has been applied to the architectural planning, vegetation and water conservancy, and other industries since 1980s. Nevertheless, the application of 3D laser scanning LiDAR in terrain surveying and mapping is innovative, which has the advantages of high speed and accuracy. Its application can reduce the working intensity and time, improve the efficiency of surveying.This study gets the point cloud data as the source of data by using this technology for exploring the method of drawing contour indirectly. 3D douglas-peucker algorithm has been proved in order to sort points. Then, Isolines can be drawn by implementing the interface of arc objects. Finally, the number of points and grid resolution will be set in different levels in order to analyze their impact on drawing Isoline.