To improve the enhancement of infrared thermal images, this paper proposes an algorithm based on an improved histogram clipping method. The algorithm determines the difference between the number of pixels in the histogram bins of the original thermal infrared image and the traditional histogram equalization image. Subsequently, based on a specific range criterion, the calculated difference of various histogram bins is divided into different blocks. Next, the histogram is redistributed, and a transform function is determined to obtain the enhanced thermal infrared image. The algorithm is based on an improved global histogram equalization method, which achieves a suitable balance between contrast enhancement, histogram shape, and detail information. The experimental results demonstrate that the average values of the peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), and mean-square error (MSE)—27.5, 0.923, and 590 respectively are better than those of other algorithms. Thus, this method effectively enhances the thermal infrared image.