In order to realize the shape from shading (SFS) under unknown light source parameters of single grayscale image, an efficient SFS method was proposed based on support vector regression(SVR) and particle swarm optimization(PSO) algorithm. Based on the SVR theory, a nonlinear mapping model was constructed between the grayscale image and its 3-D surface by researching into the SFS problem. The light source of the tested actual image should be estimated to generate the training samples corresponding to the light direction. It was important to select the proper SVR parameters for improvement on 3-D reconstruction precision, and the PSO algorithm was introduced. Finally, the case study had verified the feasibility and effectiveness of the proposed SFS method.