To date unmanned aerial system (UAS) technologies have attracted more and more attention from countries in the world. Unmanned aerial vehicles (UAVs) play an important role in reconnaissance, surveillance, and target tracking within military and civil fields. Here one briefly introduces the development of UAVs, and reviews its various subsystems including autopilot, ground station, mission planning and management subsystem, navigation system and so on. Furthermore, an overview is provided for advanced design methods of UAVs control system, including the linear feedback control, adaptive and nonlinear control, and intelligent control techniques. Finally, the future of UAVs flight control techniques is forecasted.