Abstract: Reviewing the traditional vector parallel line based and raster based method for extracting the skeleton and center of polygon, this paper presents an approach to the automatic extraction of skeleton and center based on the constraint Delaunay triangulation. The triangle in the local joint location acts as the root of the extraction tree. This paper calculates the area size split by the above triangle and makes the extension continue in the two directions whose areas are bigger. The operation repeats until all extensions ends at the vertex of polygon. The connection of all the midpoints of triangle's edges in sequence forms the skeleton of polygon. The algorithm is developed in detail and its properties are analyzed by experiment.