Abstract: The generalization of contour lines is an active issue in the field of multi-scale representation of terrains.This paper considers the contour lines as the 3D segments constructed from elevation points which are sorted in a special rule,and then selects the significant feature points from those spatial points in 3D space using the 3D D-P algorithm.Based on the spatial distribution characteristic of contour line data ses,several methods are designed and given comments on their results.It is concluded that the generalization of contour lines using 3D D-P algorithm is a promising way to meet the cartographic generalization according to its quality and speed in the generalization.