Disclosed are a method and a device for adjusting grayscale of display panel, the method includes: obtaining a current image by performing image acquisition of a display panel; identifying an nonuniform block in the current image, detecting original output brightness and original input grayscale of the nonuniform block; determining a target input grayscale corresponding to a preset target brightness according to an actual Gamma curve value, wherein the actual Gamma curve value is obtained by testing the display panel; taking a difference between the original input grayscale and the target input grayscale as a grayscale compensation value of the nonuniform block.