In order to solve the problems of thick lens thickness and uneven illumination in conventional irradiance illumination systems, a double freeform-surface lens with a distance to height ratio (DHR) of 3 is designed. According to the energy mapping theory, the light source and the target surface are meshed, the edge-ray theory and Snell's law are used to construct the double freeform-surface lens, and the actual light source is used for simulation. Compared with the single freeform-surface lens, the thickness of the double freeform-surface lens is reduced by 2.95% and the transverse size of the lens is reduced by 10.50%. The complementary feedback correction method is used to optimize the lens. The optimized single and double freeform-surface lens have 80.48% and 87.05% illumination uniformity, respectively, and the energy utilization rate is 88.61% and 91.23%, respectively. Compared with the single freeform-surface surface lighting system, the optical performance of the double freeform-surface lens is improved. For the lighting system with high DHR and small lens size, higher illuminance uniformity and energy utilization can be achieved.