Abstract: In order to study the measurement precision of DC2000 diamond proportion analyzer,the proportions of the standard round brilliant cut CZ samples are measured by the DC2000 diamond proportion analyzer.The experiment results show that the measurement precision of the DC2000 diamond proportion analyzer is almost the same as that of the international similar products,which accords with the modern diamond cut grading requirements.The requirements are that the maximum deviation of diameter and total depth is within 0.01 mm.The maximum deviation of the table,crown,girdle,pavilion and culet is within ±0.1%.The maximum deviation of angles,including crown angle and pavilion angle,is within ±0.1°.The DC2000 diamond proportion analyzer could provide accurate and reliable data for the diamond cut grading and quality testing during the cut process.