In this study, Gd O S:Tb 3+ was used as the component of the intensifying screen, and this study aims at analysis of fluorescent feature depending on the increase of tube voltage using spectrometer. When the released fluorescence was measured according to the increase of tube voltage, blue, green and red was observed, among which,F 5 which is applicable to green, was strongest. In addition, when the fluorescent of 50 kVp and 120 kVp were compared, 50 kVp was proved to release only 9.56% fluorescence of 120 kVp. In case when tube voltage which is higher than 100 kVp is used for the X-ray using Gd O S:Tb 3+ intensifying screen, the amount and strength of the fluorescence reaching the film increase drastically, so attention is demanded to get images of proper concentration.