Abstract: Different diameter of Au nano-particles were synthesized by adjustment of solvent dosage based on Frens method, then different shell thickness of monodispersed Au@SiO₂ core-shell nanostructure were fabricated. The changes of morphology and size of gold nano-particles caused by the changes of experimental conditions were observed by transmission electron microscope, and the changes of plasma resonance peak positions of gold nano-particles with the changes of particle morphology and size were observed by ultraviolet-visible spectrophotometer. With the adjustment of shell thickness, the shift rule of absorption peak position was observed by UV-Vis spectrophotometer.