Self-assembly was used to synthesize high-density Pt nanoparticles on chemically reduced graphene sheets (CRGSs). By employing 1-pyrenemethylamine (Py-CH2NH2) as the interlinker to form a self-assembled layer on the surface of graphene nanosheets via pi-pi stacking, high-density Pt nanoparticles on CRGSs were obtained. The uniform and high-density Pt nanoparticle/CRGS composite may have potential in the fields of catalysis, surface-enhanced Raman spectra, and fuel cells.