Abstract: To extract contour lines in topographic map,color topographic map is firstly segmented for achieving the binary image of brown color contour lines in this paper.Secondly,mathematic morphology method is used to filter the binary image to remove holes in contour lines.Next,contour lines are recognized before skeletoning the m utilizing deformable active contour model.Last,we have analyzed the directional field of contour lines in gap,and the n reconnected broken contour lines.The performance of the algorithm is tested on several topographic maps and compared with other algorithms.