The anodization of purple gold (AuAl2) in oxalic acid at low voltage (5 V) generated uniformly sized Au nanoparticles on the substrate. The surface of the sample showed a characteristic color after the anodization, which originated from the localized surface plasmon (LSP) of Au nanoparticles. The samples with Au nanoparticles could be applied as a substrate for the measurement of surface-enhanced Raman scattering of molecules.