A method that can be applied to two-dimensional surface shape weighted superposition is proposed, which can control the light distribution by designing free-form surfaces for extended LED light sources. Five sampling points are taken on the light source surface, which are used as five point light sources to generate five free-form surfaces, and each free-form surface data point is multiplied by a weight factor. The weighted free-form surfaces are superimposed, and the superimposed free-form surfaces are used as the initial outline. The particle swarm algorithm is used to further optimize the weight factor to obtain the optimal weight factor, and the five free-form surfaces are weighted and superposed using the optimal weight factor. The light distribution of the extended LED light source is adjusted by using the superimposed optimal free-form surface lens. The simulation result shows that this method enables the uniformity of the illuminance of the target surface to reach 75%, which is 15% higher than that generated by the initial lens on the target surface. This method has the advantages of fewer optimization variables, good surface continuity, and fast convergence speed.