Micro diamond possesses excellent physical and chemical properties.In order to expand its application field,nano silver particles were coated on the surface of micro diamond by glucose reducing complexation Ag+in silver ammonia solution. The morphology,composition and structure of composites were characterized by SEM,TEM,EDS and XRD.The properties of oxygen reduction and oxygen evolution of diamond with different content of coated Ag were studied by using rotating disk electrodes.Resultsshow that the limiting current density of oxygen reduction reaction is 4.1mA/cm
2,while the limiting current density of oxygen evolution reaction is 27.5 mA/cm
2 when the silver mass fraction is 10%.