Automatic grading measurement method of diamond color

The invention discloses an automatic grading measurement method of diamond color; the method includes steps of adjusting lighting and observing conditions so that the testing environment is consistent with environment observed by human eye; accurately positioning by a microscope zone so that the tested point is completely consistent with the measurement position point of a standard colorimetric stone when diamonds with different grains are measured; collecting an image signal and a spectral signal of a sample waist part and a pavilion and every position closing to the bottom point; contrasting a color coordinate of the measurement sample with the color coordinate of every grade standard colorimetric stone point by point; calculating the differential value between the color coordinate of the measurement sample and the color coordinate of every grade standard colorimetric stone, making the color grade of the measurement sample close to the national standard grade with the minimum differential value of the chromaticity coordinate; if the differential value of the color coordinate is consistent with two grades of standards, closing to the lower grade standard. The method guarantees the consistence of the diamond color grading and human eye observation by the automatic measurement system, simulates the traditional colorimetric environment of human eyes, and reduces the bias of the measurement system caused by different observing conditions.