Trimetallic PtxAuy@Ag nanoparticles with varying Pt/Au ratios were prepared via a seed-mediated growth process, in which Ag nanoparticles were employed as sacrificial seeds, and further evaluated as electrocatalysts for the selective oxidation of glycerol. The structures of the as-prepared PtxAuy@Ag nanoparticles were characterized by transmission electron microscopy, electron energy loss spectroscopy and UV-vis absorption spectroscopy. The electrocatalytic activity of the PtxAuy@Ag nanoparticles was extensively evaluated by various electrochemical methods including cyclic voltammetry, linear sweep voltammetry, and chronoamperometric measurements. The PtxAuy@Ag catalysts exhibit superior activity in alkaline solutions relative to acidic solutions. In acidic solutions, the Pt6Au4@Ag catalyst shows the highest current density of 0.67 mA cm(-2), which is 2.6 times that of the Pt/C catalyst. In alkaline solutions, the Pt4Au6@Ag has the highest current density of 3.1 mA cm(-2), which is 4.7 times that of the Pt/C catalyst. The products of glycerol oxidation over the catalysts at potentials of 0.5, 0.7, 0.9, 1.1 and 1.3 V were analyzed by high performance liquid chromatography (HPLC). Nine products including oxalate acid, tartronic acid, glyoxylic acid, glyceric acid, glyceraldehyde, glycolic acid, lactic acid, dihydroxyacetone (DHA), and formic acid were detected. HPLC results show that the PtxAuy@Ag catalysts tend to yield more C3 products. Notably, among the catalysts, the Pt4Au6@Ag yields the largest DHA selectivity of 77.1% at a potential of 1.1 V. The remarkable selectivity of the C3 products can be ascribed to the dominant Pt (111) facets in the Pt Auy@Ag catalysts and the synergistic effects of Pt and Au/Ag atoms.