The aim of this work is to study properties of nanostructures formed on the SiO2/Si interface by the pulsed Nd:YAG laser radiation (LR). Study of the irradiated surface morphology by AFM has shown formation of a very sharp nanohills on the SiO2/Si interface after irradiation by laser at I> 5MW/cm2. Photoluminescence of the SiO2/Si structure in visible range of spectrum with maximum at 2.05 eV obtained after irradiation by the laser at intensity I =2.0 MW/cm2. PL spectrum is strongly asymmetric with long wing in IR part of spectrum. This particularity is explained by Quantum confinement effect in nanohills/nanowires with gradually decreasing of nanowires diameter from Si substrate till top – graded band gap semiconductor. In our case the maximum of band gap is 2.05 eV which corresponds to the minimal diameter 2.3 nm on the top of nanohills-nanowire. Graded change of band gap in Si arises due to Quantum confinement effect.