The invention relates to an object elevation vectorization method and system based on three dimensional laser scanning. The method comprises the steps of regional dividing: functional regions are extracted from the cloud data of three dimensional laser points on the surface of the object through a method of small plane dividing-polymerizing; boundary extracting: geometric mutation is detected through a directional image, and then regional boundaries are used for supplementing to extract the geometric edge information of the functional regions included in the three dimensional laser points; and boundary correcting: a convex decomposition method is used for correcting the boundaries of the functional regions to complete the reconfiguration of the object elevation. The system comprises a laser scanning unit, a regional dividing unit, a boundary extracting unit, a boundary correcting unit and a three dimensional model mapping unit. The regional dividing unit extracts the functional regions from the obtained cloud data of the three dimensional laser points; the boundary extracting unit extracts the boundary information of the functional regions included in the cloud data of the three dimensional laser points; and the boundary correcting unit fits the functional regions again to correct the boundaries.