Using ion-beam-sputtering technique, Fe/Al2O3/Fe magnetic tunneling junctions (MTJ) were fabricated. Tunneling magnetoresistance (TMR) eff ect of MTJ samples has been successfully studied. The chemical composition and t he microstructural characteristics of hard-and soft-magnetic layers, insulating layer, and interface of MTJ were analyzed by X-ray photoelectron spectroscopy an d Atomic force microscopy. The dependence of MR effect on microstructure, chemic al composition, conductance, and Ｉ-Ｖ characteristic of the samples are also di scussed.