In order to solve the problem of low contrast between the target and the background and blurred details in infrared images, an improved infrared image clearing algorithm based on dark channel prior theory was proposed and FPGA was used to design the hardware system of the proposed algorithm. The dark channel image was obtained based on nonlinear filtering of the current pixel and the neighborhood data of the input image. Moreover, the correction function was used to optimize the transmission to generate a look_up table. Then the transmission was looked up in the look_up table and the proposed algorithm enhanced the image with the atmospheric scattering model, thereby reducing or eliminating the block effects and the color distortion of the sky or other bright areas generated by the traditional dark channel algorithm. The design of FPGA hardware could work with an estimated frequency of 188 MHz by occupying only 4% of LUT and 8% of I/O resources, which was much higher than the operating frequency of 27 MHz of the camera used. Therefore, the design was realized to meet the requirements of real-time application of video images.