A method for detecting grayscale compensation data of a LCD panel is provided. The method includes obtaining a first grayscale compensation data according tothephotographed screen of the LCD panel in the brightest state. According to a second grayscale value to be photographed, a predetermined grayscale compensation data scaling algorithm, and the first grayscale compensation data, a second grayscale compensation data corresponding to the second grayscale value is calculated and used to compensate a second grayscale data. The display screen of the LCD panel driving by the compensated second grayscale data is then photographed to obtain a third grayscale compensation data. The third grayscale compensation data is the grayscale compensation data of the LCD panel itself corresponding to the second grayscale value. The influence of the brightness difference of the test backlight module is eliminated. The grayscale compensation data of the LCD panel itself is accurately obtained.