A direct, quantitative analytical technique for the analysis of gadolinium, dysprosium, europium and samarium in aluminum oxide using the X-ray-excited optical fluorescence spectra is described.Rare earth elements were coprecipitated with host aluminum from acid solution as aluminum hydroxide. Precipitated hydroxide was dried after centrifugal separation and then heated in a muffle furnace at 1000°C for 2 hours. These oxides were then heated at 1450°C in an electric resistance furnace for 60 seconds.Such an impulsive heating followed by quenching, described above, prominently enhances the luminescent intensities of rare earth elements. It was shown by the X-ray diffraction method that the crystal of Al2O3 were transformed from γr-type oxide to the stable α-type oxide during the above heat treatment.Concentrations of gadolinium, dysprosium, samarium, europium have been determined by this method with detection limits ranging from 0.05 to 1.0ppm. Reproducibility was found to be 5-10%.The enhancement and suppression effect due to iron, silicon and copper were investigated and discussed.