Abstract: In order to study the aviation fuel injection and its effect to the active cooling system of a hypersonic aircraft, a numerical simulation on the flat-hole nozzle jet of RP-3 aviation fuel under supercritical state was conducted. Firstly, computational fluid dynamics (CFD) analysis was performed by software Fluent. Then a multiphase mixture model was applied to simulate the cavitation of two-phase flow. Finally, the full cavitation model was used to predict the mechanism and influence of the saturated vapor pressure of fuel on cavitation at high temperature, that is, under the inlet pressure (P_in) as high as 4 MPa, to analyze the aviation fuel injection with temperature of 333 K to 543 K under different ambient pressures (P_∞). The results show that, with the increase of fuel temperature, the saturated vapor pressure increases, while the nozzle throat cavitation and outlet flash occur gradually. With the decrease of ambient pressure, the increase of pressure drop leads to the increase of mass flow in the nozzle, and the flow in the nozzle gradually transitions from single-phase flow to cavitation two-phase flow.