Samples of porous silicon(PS) are fabricated by anodization with constantly current density,then dispersed into a colloid of Si nanoparticles(n-Si) by using supersonic.We select Al_2O_3 as a template to embed the n-Si with centrifugal force,the complex material of n-Si/Al_2O_3 can be obtained.Photoluminescent(PL) properties of PS,n-Si in acetone and in Al_2O_3 are studied systematically,and a ultrabright blue-purple photoluminescent band of n-Si can be observed.The experimental result of PL shows that there is a rather blueshift for the peak wavelength of n-Si in Al_2O_3 compared with the PS and n-Si in acetone.It has been suggested that the quantum confinement effect(QCE) may be suitably explained for the PL spectra of Al_2O_3 and n-Si.