A computer program by (EES), Engineering Equation Solver has been produced for inquiry of the fuel, clad and coolant temperatures under supercritical conditions for supercritical water reactor powered by ThO2 – UO2 mixture as a fuel. In the calculation, uniform axial heat flux and average channel were considered. The bulk fluid, clad and fuel temperatures along fuel length were obtained for supercritical pressures 26, 30 and 40 (MPa). Also the UO2 percentage added to ThO2 was varied as, 4% and 10%. It was found that the maximum fuel temperature reached 2193 (oC) in case of 4% UO2 and 2182 (oC) in case of 10% UO2, which is surpasses the industry limit of 1850 (OC).Thermal conductivity is essential parameterto understand the performance of the fuel pin under irradiation.Other important thermo-physical properties to be considered are melting point and density.Thorium and uranium oxide fuels utilized in nuclear reactors have very high melting point, but low density and they suffer from poor thermal conductivity