The ultraviolet absorption and emission spectra of Ce3+ doped phosphate glasses based on gadolinium and sodium phosphates are studied in the present work. Compared with the cerium-free phosphate glass matrixes, CePO4 doping shifts the ultraviolet absorption edge of glasses into the longer wavelength because of the 4f-5d absorption transition of Ce3+. The emission spectra correlate such red-shift with glass compositions. Explanations are based on variation in the optical basicity of glasses, which corresponds not only to the alkali content but also to the O/P ratio. The latter is proportional to the number of nonbridging oxygen in the oxyanion unit (PO4), and most likely plays an overwhelming role in the overall optical basicity of glasses.