AlPO4 mesoporous glass doped with perylene orange (PO) is prepared using two steps. The effects of dipping time and PO concentration on the fluorescent properties and molecular formation are investigated through absorption spectra, excitation spectra, and emission spectra. A slight increase in the intensity of excitation bands formed at 499 and 468 nm is ascribed to PO J-dimers aggregates as the dipping time increased from 2 to 24 h at high PO concentration (4×10^-3 mol/L). This is also the reason behind the concentration increase from 4×10^-6 to 4×10^-3 mol/L for the 16 h dipping. The excitation spectra, and the emission spectra of samples doped with PO show a slight red shift as the dipping time and the PO concentration increase. AlPO4 mesoporous glass is suitable to host the PO at high concentration.