An aspheric lens design method was presented for an application to LED collimating illumination. The method was derived from a basic geometric-optics analysis and the powerful optimization capability of particle swarm method. By using this method, a highly collimating aspheric lens based on a point source was designed. To verify the practical performance of the collimating lens, a ray-tracing method was employed to trace light rays emitted from an ideal point light source through the collimating lens. The simulation results show that the lens works well with an ideal point and the maximum half view angle of light rays emitted from the lens is 0.004 60, for a 0.8 mm×0.8 mm LED source, the maximum half view angle of light rays emitted from the lens is 4.91°, which manifests the feasibility and effectiveness of Particle Swarm Optimization(PSO) algorithm applied to designing aspheric collimating lens. Compared with the conventional design method, this design approach is more intuitive and easier to implement.