Considering that the size of collision avoidance zone is usually constant and can not make full use of the space,we proposed a method for establishing the collision avoidance zone of UAVs dynamically in real time.The collision avoidance zone is established according to the constraints of UAV maneuverability,collision zone,the relative position and the relative velocity.The influencing factors of UAV and the intruder to collision avoidance zone are considered dynamically,thus the collision avoidance zone is established more accurately with smaller airspace,which can not only avoid the unnecessary maneuvering for collision avoidance,but also make more reasonable use to the busy airspace.The simulation results show the good performance of this dynamic modeling method.