The hydrogen peroxide reduction on a silver nanoparticle modified electrode shows a CE mechanism. A diffusion oxygen layer is formed via the disproportionation of hydrogen peroxide on silver nanoparticles, and then reduced to hydrogen peroxide during electrochemistry process. Cyclic voltammetry and simulation are combined to confirm this mechanism, demonstrating the electrochemical reduction signal depends on the interacting time between silver and hydrogen peroxide via the disproportionation step before the voltammetric analysis.