Abstract: By Comparison with microwave communication, the advantages of the free-space laser communication system, such as big capacity, low power consumption, small volume and light weight, are introduced. The basic principle of the space laser communication is described. The key technologies in highpower light source, antijamming high sensitivity optical signal receiving, fast and precision capture, tracking and aiming of communication link in the space laser communication system, are put forward emphatically. The freespace laser communicationcan find wide applications in military and commercial fields and it has a great potential.