Au/Si/Au multilayer films have been prepared on n-Si(100) substrate using radio-frequency magnetron sputtering method,and then annealed in-situ at 300 ℃ for 30 min in vacuum environment.Based on results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM),it is observed that the smooth film transformes to uniformed nanoparticles after vacuum heat treatment.The average size and surface density of nanoparticles are 10-20 nm and 1×1011 cm-2 respectively.X-Ray photoelectron spectroscopy (XPS) measurements and TEM results confirm that Au element reacts with Si film and AuSi_x(x=1/2,1/7)nanoparticles with single crystallinity form.The photoluminescence (PL) properties of the sample after annealing have been analyzed at room temperature.Three peaks located at 580,628,700 nm are observed,which relate to SiO2 on the surface of the sample,defects around AuSi_x nanoparticles forming during annealing and non-bridging oxygen defects in SiO2 on the surface of sample.