The electroluminescence thin films doped with erbium, fabricated by thermal evaporation with two boats, are analyzed by X-ray diffraction (XRD). The relationship between electroluminescence brightness and microstructure of the thin films is obtained. The results reveal that the large grain size in high index plane of deposited microcrystalline film has an effect on electroluminescence characteristics of the film devices. The electroluminescence thin films doped with erbium, fabricated by thermal evaporation with two boats, are analyzed by X-ray diffraction (XRD). The relationship between electroluminescence brightness and microstructure of the thin films is obtained. The results reveal that the large grain size in high index plane of deposited microcrystalline film has an effect on electroluminescence characteristics of the film devices.