We present a perturbation study of the ground-state energy of the beryllium atom by incorporating double parameters in the atoms Hamiltonian.The eigenvalue of the Hamiltonian is then solved with a double-fold perturbation scheme,where the spin-spin interaction of electrons from different shells of the atom is also considered.Calculations show that the obtained ground-state energy is in satisfactory agreement with experiment.It is found that the Coulomb repulsion of the inner-shell electrons enhances the effective nuclear charge seen by the outer-shell electrons,and the shielding effect of the outer-shell electrons to the nucleus is also notable compared with that of the inner-shell electrons.