The foil journal bearing used in the compressor of supercritical carbon dioxide(S-CO2) Brayton cycle was taken as the research object,considering the actual physical properties of S-CO2 in the near critical region,the finite difference method was used to solve the turbulent Reynolds equation with variable density and variable viscosity,and the elastic foil deformation equation was coupled to calculate the gas film pressure distribution of foil journal bearing with S-CO2 as lubricating fluid.The influences of physical properties of S-CO2 near the critical region on the bearing capacity and friction torque were analyzed.The results show that the dramatic change of density and viscosity near the critical region has a great influence on the bearing capacity and friction torque,and the closer to the critical point,the more significant the influence is.Under the same pressure,the bearing capacity and friction torque decrease with the increase of temperature,and under the same temperature,the bearing capacity and friction torque increase with the increase of pressure.With the increase of eccentricity,the number of bearings and the aspect ratio of radial bearings,the bearing capacity and friction moment increase,while the deflection angle decreases.