A non-Markovian theory of dissipative many-electron systems in the presence of arbitrary coherent fields is presented. The new formulation is constructed via the second-quantization of a complete second-order quantum dissipation theory followed by the random phase or time-dependent Hartree-Fock approximation for electron-electron correlation. The theory is shown to be of the Fermi-Dirac thermal equilibrium statistics limit if electron-electron correlation is neglected. The key quantity is the reduced single-electron density matrix instead of the reduced density matrix of the system, which leads to the drastic reduction of numerical simulation time. The validity of the dynamic mean-field approximation is tested in a model two-electron spin-conversed system with Ohmic dissipation in the presence of excitation field. (C) 2003 Elsevier Science B.V. All rights reserved.