Abstract: The localized surface plasmon (LSP) resonance of Ag nano-sphere array was mathematically modeled, theoretically analyzed and numerically simulated with FDTD Solutions. The dependence of LSP's scattering/absorption spectra and scattering efficiency on the diameter/spacing of Ag nano-sphere array and the influence of LSP resonance on the luminous efficiency enhancement of GaN-LED were investigated. The results show that the size and spacing have a major impact. For example, as the spacing decreases, the long-wavelength LSP resonance peak gradually moves away from the stationary short-wavelength LSP resonance peak because of blue-shift; as the diameter increases, the LSP's scattering efficiency increases, accompanied by red-shift of the peaks. When matching of the two wavelengths of GaN-LED and the array's LSP occurs, the radiation luminescence is coupled into LSP via energy transfer, and the emission of some coupled energy may improve, under certain conditions, the internal quantum efficiency of GaN-LED.