Abstract: The effects of following factors on the change in thermal conductivity of supercritical fluids after being added with Cu nanoparticles were studied based on equilibrium molecular dynamics, such as the system temperature, and the size and mass fraction of particles, etc. Results show that the thermal conductivity of above nanofluids increases with the rise of temperature. The rise of both the size and the mass fraction of nanoparticles would also increase the thermal conductivity of the whole system.