Numerical simulation of cooling heat transfer to supercritical methane was investigated with Lam-Bremhorst low Reynolds turbulence model in a vertical circular tube，and the influences of flow direction，mass flow rate，heat flux and buoyancy were studied.The results showed that heat transfer coefficient of supercritical methane increased with mass flow rate increasing;heat transfer coefficient increased as heat flux increased in the gas-like region，while it was irrespective of heat flux in the liquid-like region;heat transfer coefficient was free of flow direction in the gas-like region，while heat transfer coefficient in upward flow was high than that in downward flow;density variations made heat transfer coefficient increase in gas-like region，while in the liquid-like region，heat transfer coefficient was increased in upward flow and decreased in downward flow.