A composite method combining energy and intensity mapping is proposed to address the issue of surface error caused by the irregular sampling phenomenon in freeform illumination lens design. In the combined method, the central region of the freeform lens is designed by the intensity mapping method, whereas the peripheral region is designed by the energy-mapping method. Furthermore, an iterative feedback optimization is added to scale out the application in extended light sources. As an evaluating example, a freeform lens with a 120-deg viewing angle, fitted with an appropriate number of points is designed by the proposed combined method. Compared with that designed by the energy method, the lens forms a more uniform illumination on the target surface without the appearance of a hot spot in the central region. The proposed method also exhibits superiority in extended-source design, where only a one-time optimization is needed to achieve the preset uniformity with the proper choice of coefficients.