A tunable luminescence from red to blue in Eu-doped mesoporous AlPO4 glass is achieved by adjusting the annealing temperature. With increasing annealing temperature, the increased Eu3+ ions reduction changes the luminescence of the obtained glass. The abnormal reduction of Eu3+ to Eu2+ occurs in AlPO4 mesoporous glass at relative low annealed temperatures from 600 to 800 oC in air. The presence of Eu2+ ions, which are reduced from Eu3+ by hole-electron pairs, is revealed by XPS spectra. Our results indicate the mesoporous AlPO4 glass is a suitable matrix to incorporate Eu ions as the tunable luminescent light sources or LEDs.