The modified multi-walled carbon nanotubes (m-MWCNTs)/Ag composite catalyst (Ag/m-MWCNTs) is prepared successfully by a facile in situ growth method. The physicochemical properties of Ag/m-MWCNTs are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The results demonstrate that the dispersed Ag nanoparticles are anchored on the surface of m-MWCNTs with a mean diameter about 10.6nm. The as-prepared Ag/m-MWCNTs catalyst shows high electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline media. The ORR is dominated by four-electron pathway in the limiting diffusion zone, which is similar to the commercial Pt/C catalyst. The high catalytic activity of the Ag/m-MWCNTs can ascribe to the dispersed Ag nanoparticles on the m-MWCNTs which not only facilitate the ORR process, but also may promote the decomposition or further reduction of HO2 − formed at the surfaces of the MWCNTs.