Ag/SiO2multilayers were prepared by RF magnetron sputtering. Via rapid thermal treatment, most of Ag nanoparticles move up to the surface. By changing the layer thickness of Ag and SiO2, Ag particles of different size, density and shape were obtained. The effect of factors such as size, density and shape of the Ag particle, on resonance absorption is also investigated. We change the annealing time according to the diffusion length. Ag particles with a facet parallel to substrate are obtained under adequate annealing time (17.5min). Since the atoms easily transport between particles within the facets, the radius of Ag particle decreases, and tends to a critical size. Correspondingly, the resonance absorption band becomes narrower and blueshift occurrs.