In this paper, noncovalent functionalized graphene nanosheets are prepared through solvent-exfoliation expanded graphite with the aid of supercritical (SC) CO2 and, 1-pyrenamine (PA). Then, it is used as supporting materials for platinum to investigate the potential application of the obtained nanocomposite in direct methanol fuel cells (DMFCs). Transmission electron microscope (TEM) images reveal that Pt nanoparticles are evenly dispersed on the PA-modified graphite nanosheets (PA-GNS) with an average size of 3.0 nm. The high quality of PA-GNS is also confirmed through Raman spectra analysis. PA-GNS/Pt nanocomposites exhibit better electrocatalytic activity (1.4 times) and stability (3.5 times) toward methanol oxidation than commercial catalyst JM-C/Pt The results suggest that noncovalent functionalization of GNS by PA can be a method used to create highly efficient and stable catalyst supports for methanol electrooxidation in DMFCs.