A series of Tb3+-, Ce3+-doped, and Tb3+/Ce3+-codoped silicate glasses were synthesized by melt-quenching technique. Some properties of the investigated glasses were characterized by X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), X-ray excited luminescence (XEL) and thermoluminescence (TL) spectra. The result of XPS revealed that both Ce3+ and Ce4+ ions coexisted in these silicate glasses, and energy transfer from Ce3+ to Tb3+ ions was observed under UV excitation. However, under X-ray excitation the XEL intensity of Tb3+ emission decreased dramatically upon introduction of CeO2 to the Tb3+-doped silicate glass, the higher the content of CeO2 was, the lower the intensity of Tb3+ emission was. A proposed TL mechanism was developed based the observed TL and XEL spectra. It was concluded that a cerium-related killer center formed in silicate glass with the introduction of CeO2, which competed the capture of electrons with Tb3+ luminescence center under X-ray excitation.