A new expression for photoionization cross section has been proposed based on the Beer_Lambert's law and Maxwell equations for a material.And we also proposed a function varying with the number density of the system,which includes the local field effect and the higher_order dielectric correction to the famous formula for photoionization cross section of isolated atoms,proposed by Fano and Cooper in 1968The photoionization cross sections of solid xenon have been studied by using this alternative expression which couples the macroproperty and the quantum quantity of the photoionization system,and which makes it possible for one to study the influence of induced dipoles on the photoionization.The dielectric behaviors of the matter in condensed state under several physical conditions (given the complex dielectric constants or the model of electric susceptibility of the system) are considered using our new expression for photoionization cross sections.The results show that it is reasonable in physics to calculate the cross sections of atoms in a real system by using the accurate expression.Furthermore,the more correct the model of electric susceptibility for the real system,the more accurate the cross section obtained from our formula will be.