An　enzyme-free　oxalic　acid　(OA)　electrochemical　sensor　was　assembled　using　a　platinum　nanoparticle-loaded　graphene　nanosheets　(PtNPGNs)-modified　electrode.　The　PtNPGNs,　with　a　high　yield　of　PtNPs　dispersed　on　the　graphene　nanosheets,　were　successfully　achieved　by　a　green,　rapid,　one-step　and　template-free　method.　The　resulting　PtNPGNs　were　characterized　by　transmission　electron　microscopy　(TEM),　high-resolution　TEM,　energy-dispersive　X-ray　spectroscopy,　X-ray　photoelectron　spectroscopy,　and　an　X-ray　diffraction　technique.　Electrochemical　oxidation　of　OA　on　the　PtNPGNs-modified　electrode　was　investigated　by　cyclic　voltammetry　and　differential　pulse　voltammetry　methods.　Based　on　the　results,　the　modified　electrode　exhibited　high　electrochemical　activity　with　well-defined　peaks　of　OA　oxidation　and　a　notably　decreased　overpotential　compared　to　the　bare　or　even　the　GNs-modified　electrode.　Under　optimized　conditions,　a　good　linear　response　was　observed　for　the　concentration　of　OA　and　its　current　response　was　in　the　range　of　0.1-15　mM　and　15-50　mM　with　a　detection　limit　(S/N　=　3)　of　10　μM.　Furthermore,　the　electrochemical　sensor　presented　good　characteristics　in　terms　of　stability　and　reproducibility,　promising　the　applicability　of　the　sensor　in　practical　analysis.　©　2013　The　Royal　Society　of　Chemistry.