Heat transfer research of supercritical methane in the micro-channel is of great significance to the refined design of hydrocarbon fuel precoolers. The effects of several boundary conditions， including heat flux， mass flow rate and system pressure， on the heat transfer characteristics of the supercritical methane in a horizontal microtube were experimentally studied. Besides， the enhanced heat transfer mechanism of supercritical flow was also numerically clarified. The results show that heat transfer enhancements are produced when the temperature of supercritical methane is close to the pseudo-critical temperature， and the mass flow rate and system pressure have a greater impact on the maximum heat transfer coefficient. There are two main reasons for heat transfer enhancement. One is that the large radial density gradient near the pseudo-critical point leads to the generation of buoyancy， thereby the secondary flow is generated under the combined action of gravity and buoyancy， which enhances the fluid mixing. The other is that the specific heat of supercritical methane increases sharply， resulting in the greater capacity to absorb thermal energy. Finally， an empirical correlation for the prediction of supercritical methane heat transfer in microtubes is proposed， which provides support for the refined design of hydrocarbon fuel precoolers.