Abstract: A rapid incremental surface approxi mation algorithm is proposed to establish B-spline surface fro m the unorganized point cloud.The algorithmis co mposed of four steps.Firstly,boundary data are obtained in order to set up an initial surface.Secondly,parameterization of raw data is established by projecting.Thirdly,a mask surface is designed to move on the reconstructed surface and its control points are calculated.Finally,the control points of mask surfaces and control points of the whole surface are updated. The reconstructed surface can gradually approxi mate the target surface by incrementally adding additional sampling points.For a co mplex surface,can be obtained by co mputing points'parameter and approxi mating the target surface t wice or more a satisfactory result.