The colour changeable ZnS:Mn/SrS:Ce/ZnS:Mn thin film electroluminescence devices have been prepared. The dependence of the electroluminescent emission spectra on applied voltage and frequency was studied and the reason of the different increase of the blue band and yellow band of the electroluminescent emission spectra was disscused. The reason of the different dependence of the blue band and yellow band of the electroluminescent emission spectra on frequency under different voltage was aslo disscussed.