In order to improve the energy efficiency of high power laser system of ICF and use the optical energy sufficiently, converting Gaussian laser beam into uniform beam is important. Meanwhile, the wavefront of the laser beam in the system is also significant because it affects the imaging quality at image surface and the transfer of image in multilevel magnification laser system. Starting from the Jones matrix of spheric lenses, the intensity transmittance distribution of birefringent lenses beam shaping system has been analyzed by transmission matrix. The wavefronts of different polarized states after transmission through beam shaping system are discussed. The effecting factors, such as the distances between lenses, the lens' mechanical deviation from optical axis of system, have been considered. The uniform laser beam can be obtained. In the ninth beamline of 'SG II' device, the static beam filling factor of near field can be improved from 66% to 80% by using the birefringent lens shaping system.