Abstract: 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 O2 flow of 23 and 5 sccm,the relationship of luminescent properties of Al₂O₃ :Ce³⁺ films with the amount of Ce³⁺ incorporated in the films was studied.The presence of Ce³⁺ 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 the reason for the dependence was analyzed.It is proposed that the observed light emission generated by 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.