The present disclosure relates to an adjustment method and device for a gamma circuit. In the gamma correction of the present disclosure, the brightness of the sub-pixel of each color in the white light is determined according to the brightness and color coordinates of the white light and the color coordinates of the sub-pixel of each color, the correspondence relationship between the brightness of the sub-pixel of each color in the white light and the voltage values of the sub-pixel is established, the target value of the voltage of the sub-pixel of each color is found from the correspondence relationship according to the brightness of the sub-pixel of each color in the white light corresponding to any grayscale, and then the voltages of red, green and blue sub-pixels are adjusted to the target values.