Platinum nanoparticles were formed at the surface of the poly(perfluorosulfonic) acid membrane (Nafion-117) by the galvanic reaction of PtCl₆2^- ions with Ag nanoparticles positioned near the surface of the membrane. The reduction with BH₄- ions produced Ag nanoparticles (15±4 nm size) mostly positioned near the surface of membrane due to Donnan exclusion of co-ions (BH₄-). Energy Dispersive X-ray Fluorescence (EDXRF) analysis of the membrane indicated that galvanic reaction proceeded quantitatively. Transmission Electron Microscopy (TEM) of the crosssections of membrane samples indicated that the spherical Pt nanoparticles having size 2 to 8 nm were mostly located near the surface of the membrane. The positioning of Pt nanoparticles at surface of the membrane is important for using nano-composite in catalytical application.