The invention puts forward a real-time on-line map generation method of an unmanned aerial vehicle. The real-time on-line reconstruction of the map is realized on the unmanned aerial vehicle, then, a reconstructed map is transmitted back to the ground through a high-bandwidth data transmission link, and the method is applied to the unmanned aerial vehicle to obtain a three-dimensional map of the surrounding environment of the unmanned aerial vehicle in real time and realize the positioning of the unmanned aerial vehicle. Through the method, the unmanned aerial vehicle can fly in an unknown airspace, environment information is probed and compared under a condition that the own position of the unmanned aerial vehicle is uncertain to extract and match the characteristic information of the environment so as to obtain the own positioning and carry out three-dimensional map construction. The real-time on-line map generation method can be applied to battlefield demands (such as the autonomous flight and attack of the unmanned aerial vehicle), the emergency rescue of disasters including fire hazards/earthquakes/floods and the like, the security administration monitoring of the unmanned aerial vehicle and the like. Compared with the existing method, the method disclosed by the invention is characterized in that a position drift distance, an angle drift distance and an absolute error are all in an upper level. By use of the method, more environment information is obtained. In addition, compared with a totally dense method, the method disclosed by the invention is characterized in that the experiment accuracy of the method still can achieve a use standard, and the method can be directly operated on a CPU (Central Processing Unit) and is high in instantaneity.