A numerical investigation on the melting process of paraffin wax RT44 under supergravity (5–20 g) was conducted to evaluate the effect of supergravity on the melting heat transfer characteristics. The simulations were conducted in a horizontally placed container with a constant heat flux of 5–50 kW/m2 maintained on the bottom wall under both supergravity and the earth gravity (1 g). The numerical data under supergravity are compared with those under the Earth gravity for all circumstances. The results indicate that the melting heat transfer characteristics of the phase change material (PCM) are affected by supergravity significantly (around 30%) within 20 g. With the increase of supergravity, the heating wall temperature decreases, and the liquid fraction as well as the melting rate increases. Meanwhile, the variation amplitudes of these melting characteristics decrease gradually until less than 2% at 20 g. The effect of supergravity can be attributed to the intensification of the natural convection due to buoyancy, yielding vortexes in internal flow and fluctuations of solid–liquid interface and temperature field.