Aluminum oxide film doped with cerium was deposited by the medium frequency reactive magnetron sputtering technique, under the deposition condition of constant power, 30 minutes duration, Ar and 02 flow of 23 and 5 sccm, the relationship of luminescent properties of Al2O3 ： Ce^3＋ films with the amount of Ce^3＋ incorporated in the films was studied. The presence of Ce^3＋ and the stoichiometry of these films have been determined by energy dispersive x - ray spectroscope （EDS） measurements. It is observed that the total luminescence intensity increases and the peak sits strongly depends on the cerium concentration in the films. And served light emission generated the reason for the dependence was analyzed. It is proposed that the obby luminescent center is associated with cerium chloride molecular rather than atomic cerium impurities. The crystalline structure of the sample was analysed by x - ray diffractometry （XRD）. This luminescence feature has an advantage in display techniques that require a purer blue emission.