A modification of the potential fluctuation model is proposed to explain the experimentally observed dependencies of the band shape and maximum position of the impurity luminescence in ZnSe samples highly doped with nitrogen on the doping level, excitation intensity, temperature, and decay time. In the proposed model, transitions from the localized and delocalized states of the donor impurity band and the conduction band tail appearing at high-doping level due to overlap of the wave functions of donor states, to the acceptor levels are considered instead of the donor-acceptor pair recombination. The influence of the electron-phonon interaction parameter on the spectral shape was taken into account.