Compared with a single Unmanned Aerial Vehicles (UAV)the UAV formation of has a better overall performance in cooperative detectionreconnaissance or combat.The task execution lifecycle of UAV formation is divided into six stagesincluding formation formingformation flying toward the task areaformation reconfiguration while flying toward the task areaformation reconfiguration while performing tasks in the task areaformation return and formation dissolution.These six stages are summarized in three key technical issues including formation rendezvousformation keeping and formation reconfiguration.The current situation of study on them is discussed and analyzed respectively.Finallythe future development challenges and research tendency are proposed.