The disclosure relates to a method and apparatus for converting a grayscale, and a display device, where color coordinates of respective pixel elements are determined according to grayscales corresponding to red sub-pixels, green sub-pixels, and blue sub-pixels in the respective pixel elements in image data of a frame to be displayed, and then the distances between the color coordinates of the respective pixel elements, and color coordinates of a preset white pixel on the panel, in a CIE chroma graph are determined; and the maximum grayscales of white sub-pixels in the respective pixel elements are further determined according to the respective determined distances and a preset segmentation function.