Abstract: A short residence time flow equipment for the measurement of the critical temperature and pressure of fluids was developed to determine the critical properties of endothermic hydrocarbon fuels. The short residence time (about 10s~50s) at elevatedtemperature minimized the decomposition and other reactions of fuels. Taking n-pentane, n-hexane and cyclohexane as standard reagents, the reliability of the apparatus was checked. The critical properties of endothermic hydrocarbon fuelsSimulate JP-7 and RP-3 were determined. Four estimation methods based on the volume average boiling point and relative density were also used to estimate the critical properties of the fuels. The comparisons between the experimental and predicted values indicated that the correlations suggested by API (American Petroleum Institute) and RiaziDaubert were reliable to predict the critical properties of fuels.