Thermal barrier coatings (TBCs) are used in order to protect hot section component parts from high temperature effect, extend the service life of the parts and reduce the maintenance costs in gas turbines. Thermal conductivity of TBCs directly affects the strength temperature of operating parts in hot section. The gas turbines' operating temperatures and efficiency change depending on thermal conductivity of TBCs. For this reason to determine the thermal conductivity of TBCs directly concern the turbine design. In this study, effective thermal conductivity layered structure which is composed of metal substrate and thermal barrier coating has been obtained numerically. Solutions have been performed taking conduction and radiation into consideration for different boundary conditions for TBC which have two different porosity. As a result of analyses, it has been determined that radiation boundary condition solution is 7% lower than the heat conduction solution.