This paper addresses the problem of contour line extraction from scanned topographic maps in poor condition. A novel method is developed, using knowledge of cartography and graphics to extract contours by removing other layers which overlay the contours, and reconstructing the contour lines. The contributions of this paper are the supplementation of the use of knowledge discovery for extraction on the scanned topographic maps. Examples are presented from diverse applications to show that the developed algorithm can work effectively.Facultad de Informática