The structure effects on the oxygen reduction reaction (ORR) are studied on similar sized silver nano-decahedra and nanocubes which are enclosed by (111) and (100) facets, respectively. The results show that the oxygen reduction proceeds one-step "direct" four-electron reduction on silver nanodecahedra, while two-step processes on silver nanocubes. The simulations results suggest that the different ORR catalytic activity can be interpretated by the adsorption competition between oxygen and hydroxyl on different silver facets. We demonstrate that the surface facet of silver nanocrystals is a decisive parameter to designing catalysts for ORR and other electrocatalytic reaction. (C) 2014 Elsevier B.V. All rights reserved.