Laser beam image generated by atmosphere backscattering has been widely used to monitor the laser pointing in Satellite Laser Ranging(SLR). The phenomenon that the brightness of beam image differs from sky sections influences the satellite aiming. Based on the SLR system of Shanghai Astronomical Observatory, Chinese Academy of Sciences, the mechanism of this phenomenon was figured out that the efficiency of splitter mirror was generally related to the polarization state of incident light. Accordingly, a new method was proposed that a half-wave plate was deployed in transmitting path, and rotating it realized the real-time control of different brightness for beam imaging. The model of outgoing laser polarization direction with the pointing of telescope was established. Compared with the use of splitter mirror whose efficiency is independent of polarization direction, the method is more flexible, simpler and less cost. The method can be applied in improving laser beam pointing accuracy in SLR and Signal-to-Noise Ratio(SNR) of star image etc.