Eu (1 wt%) doped 15SiO2-25B2O3-30Al2O3-30Gd2O3 oxide glasses are prepared by high-temperature melt-quenching method in air and reduced atmosphere, respectively. The properties of scintillation and photoluminescence of the two samples are compared. When the samples fabricated in reduced atmosphere are excited by the X-ray and 395 nm violet light, a 450–550 nm blue-green light beam from Eu2+ and a 615 nm red light beam from Eu3+ are obtained. The intensity ratios between Eu3+ and Eu2+ are obviously different under different excitation sources. The intensity ratio under the excitation of the 395 nm violet light is 0.02 while it increases to 1.37 under the X-ray excitation. By analyzing the phonon sideband spectra of the samples, it is found that the Eu3+ ions around the former of Si are completely reduced into Eu2+ ions, while only part of Eu3+ ions around the former of B and Al are reduced into Eu2+ ions. Further investigation about the scintillation mechanism indicates that the sensitization of Gd and the energy transfer of Eu2+→Eu3+ near the formers of B and Al increase the scintillation performances of Eu3+ ions in the reduced glass samples.