Aiming at the problems of fuzzy details and low contrast in infrared images, an infrared image enhancement algorithm based on secondary guided filtering was proposed. Firstly, the original infrared image was used as the guided image, and the guided filter was used to extract the detail information of the infrared image. Secondly, the obtained detail information was processed by guided filtering again to extract the detail information with lower noise. Finally, the original infrared image and the details of the two parts were weighted and summed to achieve infrared image enhancement. The proposed algorithm can improve the contrast and the details of the infrared images. Experimental results show that, compared with other enhancement algorithms, the average contrast and the average gradient of infrared images enhanced by the proposed algorithm is increased by 123% to 246% and 56% to 101%, respectively. The visual effect is significantly improved, and the details can be highlighted more clearly. Implementing the proposed algorithm based on field programmable gate array (FPGA) has low resource consumption. It takes up to 10.12 ms to process the single-frame infrared image with 640×512 resolution, which can meet the real-time requirements of the infrared detection system and has certain practical values.