This paper studies the influence of buoyancy on the heat transfer of the supercritical pressure level under different gravitational acceleration by the method of enhanced wall treatment combined with the RNG two equations, establishes and verifies a calculation model, and analyzes the thermal physical property of RP-3 aviation kerosene within the pseudocritical temperature. The applicability of the discriminate criterion of convective heat transfer is also analyzed. The results indicate that the drastic change of the thermal properties of kerosene within the pseudocritical temperature will cause a stronger secondary flow in the horizontal circular tube because of the effect of buoyancy lift. In the secondary flow, the convective heat transfer of the upper wall decreases, the convective heat transfer of the lower wall enhances, the friction resistance of the lower wall increases and the friction resistance of the upper wall reduces, and at last the loss of flow pressure increases. With the acceleration of gravity increases, the influence of floating lift on heat transfer and flow is more significant. From simulation it can be seen that the laws of the influence of floating lift force on heat exchange of the supercritical pressure coal oil can be described by Protopopov criterion.