Abstract: The freeform illumination lens can be designed by using the source-target map based on the energy conservation law. But the surface continuity of the lens designed by this method is relied on the integrability of the map. It is because the pre-setting map is not the real solution of the illumination problem. In order to get lens with continuous surface, in this paper, an initial lens is designed using the supporting surface method, which is constructed by certain number of Cartesian ovalpatches. The simulation results show that the desired illumination is obtained and the continue surface is maintained at the same time.