In order to solve the problems of low energy utilization, large lens size, and non-uniform illumination of existing lighting systems with the extended light source, according to the non-imaging optical marginal ray principle, this paper proposes a double freeform surface design method suitable for the extended light source and utilizes the angle difference formed by the refraction of the left and right marginal rays of the extended light source through the lens to control the illuminance distribution in the target plane. According to the design parameters, this paper calculates discrete points in the internal and external freeform surfaces, fits the contour curves of the internal and external freeform surfaces, and obtains a rotationally symmetric double freeform surface lens. In the case that the ratio of lens height to light source diameter is only 2, the paper adopts this method to design a double freeform surface lens with high energy utilization and high uniformity after numerical calculation and optical simulation. The energy utilization of the near-field double freeform optical system is 99.52%, and the illuminance uniformity is 95.81%; the energy utilization of the far-field double freeform optical system is 99.12%, and the illuminance uniformity is 93.45%. The research results show that the proposed method will guide the design of lighting systems with extended light sources.