The effects of free electrons in a plasma on a complex atom are discussed, here we are interested in the target ionAu50+ in inertia confined fusion(ICF). The results are compared with those in the case of hydrogenic ions. Accurate numerical solutions have been obtained for Schrdinger's equation through Debye screened Hartree-Fock-Slater self-consistent potential. Solutions have been computed for 28 eigenstates, 1s through n=7, l=6,yielding the energy eigenvalues for a wide range of Debye screening length Λ. As in the case of hydrogenic ions, under screening, all energy levels are shifted away from their unscreened values toward the continuum, that is, the ionization limits are shifted downward. Conclusions have been made that when Λ＞5a0， that is, in the weak screening case, Debye screening has little effect on oscillator strength, average obital radius, transition matrix elements, etc., of Au50+. For each (n,l) eigenstate, there is a finite value of screening length Λ0(n,l), for which the energy becomes zero. When Λ is sufficiently small, level crossing appears at high n satets. Optical oscillator strength for Au50+ has also been calculated, the results are compared with those under unscreened potential.