In order to better preserve the local contrast of the original color image and obtain the perceptual accurate grayscale image, a grayscale algorithm based on local contrast enhancement in contourlet transform domain is proposed. Firstly, in CIE Lab space, the conjugate gradient algorithm is used to optimize the objective function to get the global mapping function parameters, and preliminary grayscale image is obtained. Then, the multi-scale and multi-direction decomposition of color image and preliminary grayscale image are carried out by contourlet transform, local chromatic contrast ratio is used to enhance the contrast of directional detail image, and the enhanced detail image is obtained by inverse contourlet transform. Finally, the enhanced detail image is superimposed with the preliminary grayscale image to get the final grayscale image. Experiments on COLOR250 and adik database show that the proposed algorithm in this paper is superior to some typical algorithms in the existing literature, which can effectively preserve the contrast and structure information of the original image. The visual perception is natural for the grayscale image, whose subjectivity and objective evaluations are optimal.