Abstract: In order to improve visual effect of single night color image,a Retinex enhancement algorithm based on weighted least squares(WLS) was proposed. Firstly,this algorithm constructed a optimization function to prepare for the color restoration. Secondly,it processed brightness image of HSV(hue, saturation,value) color space using the WLS optimization framework which composed of brightness and gradient characteristics of night image. Then,the scene illumination could be estimated,and reflection image could be obtained. Finally,it finished the night color image enhancement after the color restoration and compensation process. The experimental results show that this algorithm has a good ability of image enhancement. Compared with other algorithms,this algorithm also has the characteristics of color restoration,Halo effect elimination,noise suppression and detail preserving.