In order to obtain a single aspheric lens for beam shrinkage, based on the law of refraction in vector form and theoretical analyses of the refraction characteristics of an aspheric surface, a new method was presented for designing a single aspheric lens used as a beam expander or a beam compressor —the comprehensive learning strategy particle swarm optimizer. A single aspheric beam-expanding lens was designed whose length is less than 170 mm and shrinkage rate is 14.16. The process of beam-shrinking or beam-expanding was simulated by using the ray tracing method. Simulation results show that a single aspheric lens can play the role of compressing beam or expanding beam, the comprehensive learning particle swarm algorithm can be used to design an aspheric lens used as compressing beam or expanding beam. A single aspheric beam-expanding（beam-compressing）lens can greatly simplify the beam expanding（beam compressing）system, and greatly improve the uniformity of output light from the expanding lens.