C-nanoparticles with a diameter smaller than 60 nm in xAl2O3-xP2O5-100SiO2(x=0.25—2) gel-glasses have been prepared by sol-gel process. The gels synthesized through partial hydrolysis of PO(OC2H5)3,Al(NO3)3·9H2O and Si(OC2H5)4 were heated at 400℃ or 450℃ in air atmosphere or from 300 to 700℃ in N2 atmosphere, in which —OC2H5 were carbonized to form nanosized C particles. These C-nanoparticles-doped gel-glasses were characterized by optical absorption and TEM.The optical absorption edge shifts to the higher-energy side as the size of the C particle decreases. This phenomenon is interpreted in terms of a quantum confinement effect of electron and hole in the C-nanoparticles. The C-nanoparticles structures were found to be amorphous carbon in the gel-glasses by electron diffraction pattern.