In the present study, the radiation properties of a high porosity fibrous medium which is used in catalytic heaters were estimated. The calculation process was based on an inverse method using pore scale simulation and two-flux model. The results showed a good agreement with available experimental results. The effects of geometrical parameters including the solid volume fraction, fibers orientation and diameter on the radiation properties were investigated. By increasing the solid share in the fibrous porous medium, the extinction coefficient increased, in which the absorption growth rate was higher than the scattering growth rate. The effect of the fibers angle on the scattering was greater than its effect on the absorption. For each porosity, an extinction coefficient could be defined in which, by increasing the fibers diameter, the extinction coefficient would not be reduced any more. The solid volume fraction, fibers diameter and orientation were found to be the most effective geometric parameters on the radiation properties, respectively.