We propose a general method to calculate the full Green's function of multielectron atomic ions. The key point exists in the usage of L2 integrable functions as a complete basis set in a finite region together with an optical potential to guaranty the outgoing scattering boundary condition. In such a way, the cumbersome procedure of adjusting boundary conditions in solving the differential Schrödinger equation is avoided. To show the validity of the method, we studied the radiative recombination involving dielectronic recombinations of Be-like Hg (Z=80) ions. The radiative damping effect is taken into account naturally in the present method. The calculated results reproduce well the asymmetric line profile observed in the experiments.