A grayscale voltage calibration device comprises: an adjusting circuit, configured to receive an actual grayscale voltage value of a grayscale output from a source driver IC, compare the actual grayscale voltage value with a theoretically determined voltage value of the grayscale, and adjust the actual grayscale voltage when the comparison result indicates that the actual grayscale voltage is not equal or close to the theoretically determined voltage value; and a verification circuit, configured to verify whether the adjusted grayscale voltage value is equal or close to the theoretically determined voltage value, and feedback the adjusted grayscale voltage value as a target voltage value to be input to a display panel of the display device to the source driver IC if yes, otherwise, control the adjusting circuit to further adjust the adjusted grayscale voltage value.