The present disclosure discloses a method and device for correcting display brightness of a display module and a display module. The method includes: receiving target brightness of the display module; determining target brightness components of sub-pixels of various colors corresponding to the target brightness according to a chromaticity coordinate of the target brightness and characteristics of luminescence of the sub-pixels of various colors in the display module; determining an initial gamma register value according to the target brightness components of the sub-pixels of various colors corresponding to the target brightness; performing gamma correction on the display module according to the initial gamma register value, and detecting the display brightness; and in response to determining that a difference value between the display brightness and the target brightness exceeds a first preset range, correcting the display brightness by adjusting the initial gamma register value according to the difference value.