Spinel specimens deposited with a thin heavy metal (Cu，Au) film were implanted with inert-gas-ions and annealed in vacuum subsequently. The surface-plasmon-resonance-absorbance peak corresponding to metallic nanoparticles in the dielectric matrix was observed in the ultraviolet-visible absorbance spectra，indicating metallic nanoparticles were formed in the spinel specimens. The influence of the thickness of the metallic film deposited on the spinel specimen surface on the nanoparticle formation is evident besides the effect of annealing temperature.