Based on a spatial energy partition mapping, a design method of LED illumination lens is demonstrated to realize high-efficiency and high-uniformity illumination on the target screen. This method first performs the differential of the radiation source, and then establishes a relation mapping with the prescribed lighting. Lens structure can be finally achieved by solving a group of partial differential equation. For design demonstration, a high-power LED with the emitting area of 1.2 mm×1.2 mm is applied. The designed lens could offer an effective lighting on the target with the collection efficiency over 99% and the spatial uniformity of 91.67%. Simulation results agree well with the theoretical derivation.