Li reacts with N2 at room temperature. In order to activate Li, the mechanical milling of Li with stable metal oxide, namely, Al2O3 and MgO, using a high energy vibrating ball mill was performed. In the case of Li-MgO system, it reacts with N2, but hardly reacts with O2. The reaction with N2 generally produces Li3N, while for some vigorous reactions the Mg3N2 is produced as the major phases. In the case of Li-Al2O3 system, reactivities with both N2 and O2 are high. The difference is explained in terms of the reaction mechanism and the Li state.