The embodiment of the invention provides a testing device, a method of the testing device, a display device and a display method of the display device, and relates to the technical field of display. The testing device, the method of the testing device, the display device and the display method of the display device solve the problems that distribution of brightness of a backlight source is not uniform caused due to the fact that the light mixing distance of an LED lamp is shortened. The testing method includes the steps of displaying a test image under the action of the backlight source, collecting brightness values of all pixels of the test image, and obtaining at least one compensation value according to light distribution data, wherein the compensation value serves as the basis for compensating for the brightness values of the pixels of the test image to standard brightness values.