We prepared aSi:H/SiO2 multilayer by using layer by layer deposition of aSi:H sublayer and insitu plasma oxidation in the plasmaenhanced chemical vapor deposition system. Based on the constrained crystallization principle of aSi:H sublayer, we employed krF excimer laser to irradiate aSi:H sublayer and crystallize it. The results of Raman scattering spectroscopy and electron diffraction show that nanocrystal silicon (ncSi) has been formed within the asdeposited aSi:H/SiO2 multilayer, and that the size of ncSi can be controlled precisely according to the thickness of aSi:H sublayer. We also studied the photoluminescence(PL) property of the sample and the effect of laser energy density on PL.