The key technologies for generating sketch contours are researched on which the features such as extrusion, revolution and sweeping are reconstructed. First the planar data points are arranged in sequence by improved least distance arrangement algorithm. The feature points are extracted in terms of estimated curvatures and their changes. The types of feature points are identified by use of Adaptive K-Curvature Function. The types of planar curves are judged by Projective Height Function. On basis of feature point treatment the dividing points to segment curves are determined, which provides the foundation for constraint-based reconstruction of sketch contours in reverse engineering.