Surface-plasmon-enhanced GaN-LED was proposed based on the multilayered rectangular nano-grating, which was deposited by periodic raster silver thin film in the gas material. A model was theoretically established, which was enhancing the internal luminous efficiency of LED, the SPPs radiant matching and the SPPs radiant declining. The experiment shows that the structure of the deposited silver thin film can improve the luminous efficiency because of the SPPs enhancement. Polarized mode of the emergent light has no effect on the luminous efficiency of LED; Metal raster absorptivity will achieve the peak if the duty ratio is about 0.87; SPPs potentiation can dramatically improve the luminous efficiency and nonlinear process. The research on the improvement of the LED luminous efficiency has theoretical and practical significance.