We investigate the effect of localized surface plasmon(LSP) on efficiency of phosphor. With energy matching between red phosphor and LSP of multi-core Au-SiO2 nanoparticles, efficiency of phosphor was improved. With optimization of density of Au nanoparticles and thickness of spacer layer without agglomeration of nanoparticles, efficiency of red phosphor is improved by 18 % compared to isolated red phosphor. This work can provide a solution to fabricate high efficiency, high color rendering index and wide color gamut (of white LED).