The invention provides an image enhancement method, an image enhancement device and a display device. The image enhancement method comprises the steps that a first color space of an original image is transferred to a second color space containing brightness information, and the brightness information of the original image is extracted; an optimum transformation parameter value of a grey level transformation function for image enhancement is determined through an optimizing algorithm according to the brightness information; a transformation curve of the grey level transformation function is constructed according to the optimum transformation parameter value, the brightness information is subjected to enhancement processing according to the transformation curve, and then the enhanced brightness information is obtained; the enhanced brightness information is transferred from the second color space to the first color space, and then a final enhanced image is obtained. By the adoption of the image enhancement method, optimum transformation parameters of the grey level transformation function can be automatically determined through the optimizing algorithm, and consequently self-adaptive enhancement of the image is achieved.