An electromagnetic immune Free Space Optical Communication (FSOC) system for an Unmanned Aerial Vehicle (UAV) command and control link is introduced in this paper. The system uses the scheme of omnidirectional receiving and ground scanning transmitting. It has a strong anti-turbulence ability by using a large area detector and short-focus lens. The design of omnidirectional communication improves the ability of anti-vibration and link establishment. Pure static reception has no momentum effect on the platform. The receiver is miniaturized under no use of a gimbal mirror system, beacon camera system, Four-Quadrant Photodetector (QPD) and multi-level lens system. The system can realize omnidirectional reception and the communication probability in 1 s is greater than 99.99%. This design strengthens the ability of the FSOC system, so it can be applied in the UAV command and control, the satellite submarine communication and other occasions where the size of the platform is restricted.