Fe-O/AlOx/Fe-O tunnel junctions were prepared by reactive magnetron sputteringunder mixed working gas Ar+2%O2. The insulating AlOx layer of 1-2nm thicknesswas sputtered directly from Al2O3 target. Electrode layers were made of 80at.% ironand 20at.% oxygen. Bottom Fe-O electrode deposited on glass substrate annealedat 473K at the pressure of 3× 10-4Pa for an hour shows disparate crystalline grainstructure, lower electrical resistance and coercivity compared to the as-deposited topelectrode. Only crystalline structrure of α-Fe is observed in both electrodes. Largetunnel magnetoresistance in large Fe-O/AlOx/Fe-O junctions of 1cm2 is observed atroom temperature and the Ⅰ-Ⅴ characteristic curve of the junction shows that thebarrier of the junction is of high quality.