A luminance compensation method and a luminance compensation device of a display device, and the display device are provided. The luminance compensation method of the display device, includes: obtaining an input grayscale value of one of a plurality of sub-pixels corresponding to the display device of an input image, and obtaining a functional relationship between a compensated grayscale value and the input grayscale value corresponding to the sub-pixel; obtaining the compensated grayscale value corresponding to the sub-pixel by using the functional relationship, and performing luminance compensation on the sub-pixel according to the compensated grayscale value; and executing the above operations repeatedly for each of the plurality of sub-pixels of the input image.