We investigate the GaN-LED epitaxial wafers whose central wavelength is 650 nm and propose a kind of bottom-emitting surface-plasmon-enhanced LED to improve its emission efficiency. This LED includes a SiO2 layer of low refractive index and a silver film coated on the sinusoidal wavy-patterned p-GaN layer in sequence. The Ag film is used to enhance the internal quantum efficiency and the SiO2 layer is employed to further improve the reflectivity of the upper surface of GaN-layer. And the transmissivity through the sapphire substrate whose thickness is optimized is very high. The emission efficiency of this structure is raised greatly.