In response to the need for target highlighting in infrared night vision aiming systems, a method for extracting target contours from infrared images is proposed. This method is based on real-time infrared imaging systems, and after analyzing the characteristics of infrared target images, the shortcomings of the application of Sobel operator in infrared images are improved through operations such as Gaussian filtering pre-processing, contrast enhancement, and dark background edge removal. The simulation has achieved accurate extraction of target edges in infrared images. The application effect of the algorithm in the infrared night vision aiming system is verified on a Field-Programmable Gate Array (FPGA) real-time processing platform. The results show that the method for extracting target contours in the infrared night vision aiming system has good edge extraction effects in the FPGA real-time system and has achieved significant target highlighting performance with less than 2% hardware resource occupation.