Abstract: Triangular silver nanoplates have been prepared by seed-mediated growth with CTAB as soft template, and their morphologies, chemical components and optical absorption properties have been characterized by TEM, EDX and UV-Vis. The results indicate that the as-prepared nanoparticles are single-crystal Ag with face center cubic structure. The nanoplates have triangular shape and their average edge length increases from 20 nm to 100 nm by lowering the adding amount of Ag seed. CTAB exists as a thin film capping the Ag nanoparticles and prevents them from being oxidized. Three peaks appear in the absorption spectra of the Ag nanocolloid, and they can be ascribed to different modes of surface plasmon resonance of the nanoplates. The Ag nanoplates selfassemble into twodimensional array when