The present invention provides a device and a method for compensating a voltage of a primary color subpixel, and a display device. The voltage compensation device includes: a grayscale determination module for determining whether a display grayscale value corresponding to a data voltage of the primary color subpixel is larger than a preset grayscale value; a first compensation module for performing voltage compensation on the primary color subpixel according to primary color mura information acquired in advance in a primary color test picture, when the display grayscale value is determined to be larger than the preset grayscale value; and a second compensation module for performing voltage compensation on the primary color subpixel according to gray mura information acquired in advance in a gray test picture, when the display grayscale value is determined to be equal to or smaller than the preset grayscale value.