The disclosure discloses a compensation method for a display module including: using a first group of program code to make the display module display a first greyscale value; acquiring a screen image to determine a normal display area and a poor display area; changing an output voltage for the poor display area, and recording a compensated output voltage that makes the luminance of the poor display area identical with that of the normal display area; and writing program code corresponding to the compensated output voltage into the first group of program code. The disclosure also discloses a compensation device for a display module.