ing at the problems of information loss, unclear region and fog occlusion in foggy images, in this paper, a Gaussian pyramid transform Retinex image enhancement algorithm based on bilateral filtering is proposed to improved the contrast of foggy image. First, an improved mathematical model of bilateral filtering function based on spatial kernel function and pixel difference is established. Second, the input image is converted into HSI (hue, Saturation, intensity) image, and the improved bilateral filtering function is used to replace the Gaussian function in the original algorithm. The reflection component is extracted from the luminance image (I color space) to obtain a reflection image with edges retained and unaffected by brightness. Finally, color images of different scales are obtained through Gaussian pyramid down sampling, the images of different scales are enhanced by improved Retinex algorithm, and the image is reconstructed based on Gaussian Laplacian algorithm to improve the image contrast. Experimental results show that the algorithm can effectively enhance the contrast of the image, and the color of the processed image conforms to the observation effect of human eyes.