Abstract: The image is often significantly degraded by fog and mist and its value is greatly reduced.According to color constancy of Retinex theory,the fog degradation can be eliminated by extracting illumination component.Shortages of fog images proccessed by MSR algorithm were pointed out and an improved algorithm combining the resulting image by MSR algorithm with the original image,which uses logarithm component and color information of the original image to keep global contrast and recover colors of flat areas.A method to enhance details of fog images further was proposed: Firstly,the resulting image is obtained by recombination of the output of MSR with the original image with enhanced edges.Secondly,color components of the resulting image are respectively clipped,then all pixels are scaled up to the dynamic range of display device.The experiment result showed that the algorithm can effectively remove fog degradation from images.