Fe3O4(magnetite) having half metallic property attracts great attention material with high curie temperature in spintronics. Fe3O4 thin films and nanowires were grown onto c-Al2O3(0001) at various substrate temperatures. Fe3O4 films deposited from 300 to 600℃ are influenced by thermal stress induced from mismatch of thermal expansion coefficient between Fe3O4 and Al2O3 (0001) substrate. The Fe3O4 nanowires grown at 640℃ showed a diameter of 130 nm and a length of 2-10 μm. The nanowire arrays fabricated by pulsed laser deposition technique have high coercivity(Hc) of 608 Oe and Squareness(Mr/Ms) of 0.68 in perpendicular direction.