A new simple drying process was developed in order to prepare a metallic nanocatalysts/Nafion for self-humidifying membrane in a proton-exchange membrane fuel cell (PEMFC). Metallic precursors such as platinum(ll) bis(acetylacetonate) or palladium(ll) bis(acetylacetonate) was sublimed and simultaneously penetrated into the surface of a Nafion film. And then it was reduced to Pt or Pd nanoparticles beneath the film surface without a special reducing agent in a glass reactor of N2 atmosphere at 180 degrees C for 5, 10, 30 and 60 min, respectively. The morphology and distribution of the Pt or Pd nanoparticles were observed by transmission electron microscopy (TEM) and elemental analysis was carried out by an energy dispersive spectroscopy (EDS), and we found that the penetration depth of the metallic nanoparticles and the particle sizes increased with increasing exposure time to the metallic precursors, and the particle size at the surface area was larger than that at the deeper area.