A new fabrication method of a-Si∶H/SiO2 mutilayers (ML) is successfully employed by using layer by layer deposition of a-Si∶H sublayer and in situ plasma oxidation in a plasma-enhanced chemical vapor deposition system. Based on the constrained crystallization principle of a-Si∶H sublayer, the size-controlled nc-Si/SiO2 ML was obtained by the crystallization treatment including a rapid thermal process and furnace annealing. Blue photoluminescence is observed in the crystallized a-Si∶H/SiO2 ML at room temperature. The structure property of the nc-Si/SiO2 ML is investigated by transmission electron microscopy and Raman scattering spectroscopy. The origin of the blue-light emission is briefly discussed in combination with PL and absorption measurements.