Aiming at the requirements of online target recognition and positioning in UAV autonomous reconnaissance mission, this paper firstly summarizes relevant research results in the field of target recognition in UAV reconnaissance. Then, the implementation principle of Faster RCNN is introduced and the improvement is made according to the task requirements. After that, we introduce the correlation algorithm of image mosaic and propose the target relative positioning algorithm. Finally, a complete outdoor test procedure is designed to verify the proposed method. The results show that the improved target detection network in this paper can achieve the recognition accuracy rate of 85.6% and the recognition speed of 35 frames per second, and the proposed relative positioning algorithm can achieve the average positioning accuracy of 0.702m, which can meet the task requirements of the online target identification and positioning of reconnaissance UAV.