The energy transfer process of translationally hot oxygen atom O(D-1) by inelastic collision with N-2 molecule, fast O(D-1) + N-2 --> slow O(D-1) + N-2(v,J), has been studied by means of quasi-classical trajectory calculations on the ab initio fitted potential energy surfaces (PESs). The surface hopping procedure was included in the trajectory calculations by the Landau-Zener model in order to consider contribution from the reactive trajectories, i.e., the electronic energy transfer process O(D-1) + N-2 --> O(P-3) + N-2(v,J). Inelastic collisions occurring on (1)A’ and/or (3)A’ surfaces were only considered in the present study. The results suggest that the cross section for the translational energy transfer process increases with increasing collision energy. Efficiency of the energy transfer from translational to internal modes by a collision was calculated to be 0.45 at a collision energy of 10.0 kcal/mol. The energy relaxation processes of translationally hot O(D-1) in the upper stratosphere are discussed on the basis of these theoretical results.