A　graphene-Nafion　matrix　modified　glassy　carbon　electrode　(Graphene-Nafion/GCE)　was　developed　for　the　determination　of　organophosphorus　pesticides　(OPs).　Graphene　nanosheets　were　synthesized　chemically　by　the　Hummers　method.　The　electrochemical　properties　of　the　Graphene-Nafion/GCE　were　investigated　by　cyclic　voltammetry　and　square-wave　voltammetry.　It　was　found　that　the　graphene-Nafion　matrix　not　only　enhanced　the　adsorption　to　OPs,　but　also　improved　the　sensitivity　of　the　OPs　determination　due　to　the　synergistic　effect　of　graphene　nanosheets　and　Nafion.　Methyl　parathion　was　selected　as　a　model　of　OPs.　Compared　to　the　unmodified　electrode,　the　peak　current　obviously　increased　and　the　reduction　peak　potential　positively　shifted.　Under　the　optimum　conditions,　the　response　current　of　stripping　voltammetry　was　linearly　related　to　the　concentration　of　methyl　parathion　over　the　range　from　0.02　to　20　mu　g/ml　with　a　detection　limit　of　1.6　ng/ml.　The　sensor　was　successfully　applied　in　the　determination　of　methyl　parathion　in　vegetable　samples　by　the　standard　addition　method.