Abstract: This paper deals with the computer simulation of manual cartographic generalization using automatically pre-processed raster data of contours by comparing the two-dimensional curvatures to search for the feature points on the contour,filtering out the valley points,tracing the valley lines,deciding the valleys to be remained on the basis of evaluating the importance of each valley and measuring the mean distance of every couple,and generalizing the valley curves in group.Results of preliminary experiments are also included.