Abstract: Laser beam expander is used to compress the laser divergence angle, in order to reduce the energy losing in long distance scanning acquisition system. To meet the requirements of the laser communication experiment, a laser beam expander system was designed. The system has 10 times magnification and 48 40 working field, which is used in 1 550 nm, 1 064 nm, 800 nm and 632.8 nm laser wavebands(632.8 nm waveband is mainly used for system test). After the calculation of primary structrue parameters and the optimization by Zemax, four conic mirrors were used to compose the system. Considering the tolerence, the system-s maxium wavefront aberration(WFE) is 0.095(=632.8 nm) that satisfies the requirement of the RMS of WFE ＜0.1. It has a total size of 9010060 mm3 and transmission of about 92%，which also meets the 85% transmission demand.