Abstract: A novel high-temperature flow calorimetric system of conduction type was designed, and built in which chromatogram was used for on line analysis.The thermal constant at 700 ℃ of the calorimeter was calibrated by the sample electric energy method, and the average result was 21.67 W•mV^-1.The accuracy of the equipment was also validated by standard such as heptane, the result showed that this equipment was reliable.The heat sink values of six kinds of fundamental endothermic hydrocarbon fuels at 700 ℃ were determined by using this equipment.The results showed that the heat sink of NJ-4 was the highest one which is 3.0 MJ•kg^-1, and that of NJ-6 was the lowest one, only 2.6 MJ•kg^-1.