The present invention discloses a gray scale adjustment method and device for a display panel. The method includes: performing an image acquisition on the display panel to obtain a current image; identifying a relationship between an average value of gray scale values of all pixels in a set range in the current image and a target value by a distinguishing method, in order to identify an uneven block in the current image; detecting an original output luminance and an original input gray scale of the uneven block; determining a target input gray scale corresponding to a preset target luminance according to an actual gamma curve value obtained by testing the display panel; and taking a difference between the original input gray scale and the target input gray scale as a gray scale compensation value of the uneven block.