The problems of the large beam divergence angle and short detection range in the launch system of laser proximity fuze are investigated. By analyzing the optical structural characteristics of large field laser proximity fuze, combined with characteristics of distance influencing factors, and according to aspheric optical design theory, multilevel aspheric collimating lens are designed using Zemax software. Simulation results show that, comparing with single aspheric collimating lens, multilevel lens increase the brightness of the center of irradiation nearly 10-fold, and the spot size decreases and energy concentrates. At last, aspheric lens is processed and experiment has been done, the results show that this collimating system can compress spot size effectively, and the system detection range is improved.