Se2- color centers and CdSe/Cd1-xZnxSe quantum dots (QDs) were formed in silicate glasses, respectively, by carefully adjusting the content of Al2O3. The absorption coefficient and broad visible emission at 400-700 nm of Se2- color centers increased firstly and then decreased upon increasing concentration of Al2O3 from 0 to 5 mol. %. With 2 mol. % Al2O3 adding, the band edge emission centered at 497 nm from CdSe QDs in glasses was observed after heat treatment. Raman spectra and TEM characterization confirmed the formation of CdSe/Cd1-xZnxSe QDs. The small amount addition of Al2O3 had a significant effect on the formation of Se2- color centers and precipitation of CdSe/Cd1-xZnxSe QDs in glasses due to its complicated effect on the network structure and optical basicity of the glasses.