Aiming at the actual image brightness/contrast in fog environment，an overall gray level tensile and local contrast enhancement algorithm to improve the image brightness and contrast is proposed in this paper. The image removal algorithm based on dark primary color prior is used to remove the haze effect often encountered in video surveillance. In order to eliminate the blocking artifact，the image is divided into the smallest blocks，that is，the dark primary color is extracted for each pixel，and the adjacent similarity principle is used to correct the dark primary color. MATLAB simulation shows that the improved algorithm can remove haze from the image. Finally，the software development of DaVinci DM6467 based image enhancement algorithm is completed，and the output，switching and image enhancement of 4-channel video are realized. Enhanced image，its SSIM indicator can be increased by more than 50%. The system can effectively remove the effects of haze on the image to meet the needs of image dehaze enhancement.