Abstract: An effective image contrast enhancement method based on partial differential equations is proposed to improve the image quality degraded by the uneven distributed illumination in the image.In order to amplify the details,we adjust the distribution of image gradient by histogram equalization of gradient field firstly and then reconstruct the result image from modified gradient field in least square sense.With the introduction of Lab color space,the new method is extended to color image enhancement.In terms of numerical scheme for Poisson equation,a more efficient scheme is proposed according to the character of the Laplacian operator,which avails the programming and computational efficiency.Experimental results show the effect and efficiency of our new model in improving the image contrast caused by uneven illumination.