Sharing airspace with manned aircrafts in different degree of cooperation is the future trend of unmanned aerial vehicle (UAV) operations, and collision avoidance issues become key challenges hindering UAV from flying beyond segregated airspace. Requirements of autonomous collision avoidance for UAV are analyzed from the perspective of the particularity of the UAV collision avoidance combined with current layered aircraft collision avoidance strategies, and framework of UAV autonomous collision avoidance system is proposed. Two key techniques and their application scope and main issues of UAV autonomous collision avoidance are analyzed and discussed inductively, i.e. sensor technologies and collision avoidance algorithms, and on this basis manage system of UAV autonomous avoidance is proposed. Finally, development trends of UAV autonomous collision avoidance techniques are explored.