[en] When we perform experiments or numerical calculations on heat, momentum and mass transfer, it is necessary to know thermal properties of fluids. However, as there are few experimental data of the thermal properties for multi-component gas mixtures, we need to evaluate the thermal properties of the multi-component gas mixture to investigate thermohydraulic phenomena. The equations for thermal properties are useful for numerical calculations in the gas mixture with the properties dependent on gas temperature, pressure and concentration of gas species. This paper deals with the thermal properties of the multi-component gas mixture that is produced at a pipe rupture accident of high temperature gas cooled reactors. Particularly, transport properties were calculated from a theoretical and an empirical correlations. As most of the equations in the present paper are expressed as general formulas, the thermal properties of other gas mixture can be simply evaluated by the equations. (author)