Automatic aerial refueling (AAR) is the advanced form of aerial refueling, its application can greatly extend the efficiency of unmanned aerial vehicles. And it has been a new research area of aeronautics in recent years. In this paper, a comprehensive review is made of state of art research in automated aerial refueling. By introducing the characteristic of AAR, the two existing methods of aerial refueling are compared with each other. The basic principles and technical approaches are discussed in detail. Three parts such as selection of sensor, controller design, simulation and testing, are particularly discussed to introduce the up to the minute investigation. Some important topics, including the sensor precision, maneuver rendezvous and docking strategy, cooperated operation, command and communication, and navigation algorithm are put forward as the fundamental problems and technical challenges in future aerial refueling research. Finally, the technologies which could be exploited primarily and come true in near future is pointed out.