It is very necessary to defog the images captured in the foggy days，because the scattering effect of atmospheric suspending particles will lead to serious image degradation，which directly influences the visual effect and its application range. Based on the principle of dark channel priority，a segmentation model is introduced to estimate a image transmission map precisely and fast in local area， and then the atmosphere scattering model is applied to defog the images，and the image contrast after defogging is enhanced by histogram stretching. Experiment results show that the proposed algorithm efficiently removes the influence of the fog to the image with high processing speed and wide application range.