In this article, Pt nanoparticles protected by 1-dodecanethiol (DDT) were self-assembled on iron surface forming mixed self-assembled films. Those nanoparticles were prepared in aqueous solution and transferred from water phase to toluene phase. The self-assembled films of nanoparticles protected by DDT were prepared on iron surface. The nanoparticles were characterized by UV-vis spectroscopy. Electrochemical impedance spectroscopy (EIS), polarization curves, X-ray photoelectron spectroscopy (XPS) were applied to characterize the self-assembled films on iron surface.