Endothermic Hydrocarbon Fuel-Tianjin University (EHF-TU) is one advanced propellant and fractionated from RP-3 extensively used in China. The density of propellant EHF-TU at supercritical pressures is measured using the flow conservation method. The measurement covers temperatures from (303 to 765) K and pressures of (3 to 7) MPa using three tubes with different sizes, and the density varies from (759 to 134) kg•m −3 . The n-decane is used for calibration, and the relative uncertainty of density measurement is 1.1%. A series of measures were adopted to improve the measurement accuracy including flexible sizes of test tubes, the lumped parameter method, and the advanced data process. The results indicate that density decreases with the decline of temperature and pressure. Dramatic variation of density occurs in the pseudocritical region at 3 MPa pressure. Density data is fitted using polynomials, and the average absolute deviation (AAD) between the experimental data and the fitted data is 0.7%. Additionally, the volumetric thermal expansion coefficient of EHF-TU is calculated using the polynomials.