In order to solve the problem of big beam divergence of laser diode，according to the principle of geometrical optics，mathematical models are built respectively for the different divergence in the sagittal and radial directions，and an aspherical lens with two different orthogonal aspherical surface type is designed.Simulations are carried out with the ZEMAX optical design software.After passing through the designed aspherical lens，the divergence angles 35 ° and 7.5 ° of the fast and slow axis directions of the laser diode are compressed to 1.8mrad 0.84mrad respectively.The total power received 10m from the light source is 0.497W，light energy utilizing efficient is as high as 99.4%.The results show that the aspherical lens with a different face in mutually perpendicular directions has a good effect on laser diode collimation.