Abstract: An inverse problem method of transient combined radiative conductive heat transfer is proposed to determine the thermal conductiviity of non gray semi transfarent material is proposed on the basis of the laser impulse method for the non transparent material.The one dimensional semi transparent sample with black interfaces is submitted to an external rectangle pulsed irradiation and the temperature response occurs in the sample.There are two peaks in the temperature response of non incident surface.The thermal conductivity can be determined by this method,provided to temperature responses at the two surfaces are measured and the radiative properties of semi transparent material are known.The control volume mothod and the spectral band model are used in the numerical calculation.The divergence of radiative flux is treated as the source term of the energy equation.In the inverse problem method the golden section method is applied to searching for the optimum of the solution.The temperature response of the non irradiated surface is taken as a given condition and the temperature response of the irradiated surface as a restricted condition.Two cases are considered,i.e.the case of constant thermal conductivity and the case of thermal conductivity varying with temperature in a linear relation.The numerical simulation has been carried out.It is proved that this method is feasible.The influences of the searching region and the measurement errors are also discussed in this paper.