Ag/C catalysts with different Ag particle-size distribution were prepared by Ag(I) single crystal reduction method (Ag(I) SCRM) and physically characterized. Their electrochemical performances were investigated by using Ag/C as O-2 reduction catalysts in alkaline electrolyte. The results showed that the electrocatalytic activity of Ag/C catalysts prepared by the Ag(I) SCRM was significantly enhanced compared with that of Ag/C catalysts prepared by Ag2O reduction method (Ag2O RM) under the same content of Ag. The cyclic voltammetry indicate that the larger Ag particles are favourable to the four-electron reduction of O-2, the finer Ag particles are favourable to the two-electron reduction Of O-2; the overpotential of four-electron reduction is higher, the overpotential of two-electron reduction is lower. (C) 2009 Elsevier B.V. All rights reserved.