The instrument can quickly and accurately determine the cetane number of diesel fuel, and has the characteristics of short detection time, accurate detection results, low noise, and low operation and maintenance costs. The machine has its injection system (patent), which can greatly improve the accuracy of diesel cetane number determination. A large amount of test data shows that the instrument fully meets the requirements of ASTM D613, ASTM D6890 and GB/T386 standards. The instrument has a wide detection range and accurate data. It is suitable for various conventional biodiesel, petrochemical diesel, sand-based oil, fuel oil, and special fuel. And various fuels added with nitrate and hexadecane oxide enhancers. The entire testing process of the instrument can be completed automatically within 20 minutes (including all preliminary preparation time). After each test, printing all test and statistical analysis results is suitable for use by research units, laboratories, oil refineries and other related departments.