Cu-doped and Cu/Al-codoped high silica glasses (HSGes) are prepared by doping Cu 2+ ions or codoping Cu 2+ ions and Al 3+ ions in porous glasses and then sintering at 1200°C in air and the reduction of Cu 2+ ions is observed in Cu/Al-codoped HSGes. With increasing the Al/Cu molar ratio, the color of the samples changes from brown to colorless gradually. Strong and broad glaucous emission from the monomer and dimmer Cu + ions are observed when exciting the colorless samples with ultraviolet light. Absorption, photoluminescence, electron spin resonance (ESR) spectra and X-ray photoelectron spectroscopy (XPS) are carried out to investigate this phenomenon. The mechanism of this change is presented.