A　novel　nonenzymatic　H　2　O　2　sensor　based　on　a　palladium　nanoparticles/graphene　(Pd-NPs/GN)　hybrid　nanostructures　composite　film　modified　glassy　carbon　electrode　(GCE)　was　reported.　The　composites　of　graphene　(GN)　decorated　with　Pd　nanoparticles　have　been　prepared　by　simultaneously　reducing　graphite　oxide　(GO)　and　K　2　PdCl　4　in　one　pot.　The　Pd-NPs　were　intended　to　enlarge　the　interplanar　spacing　of　graphene　nanosheets　and　were　well　dispersed　on　the　surface　or　completely　embedded　into　few-layer　GN,　which　maintain　their　high　surface　area　and　prevent　GN　from　aggregating.　XPS　analysis　indicated　that　the　surface　Pd　atoms　are　negatively　charged,　favoring　the　reduction　process　of　H　2　O　2　.　Moreover,　the　Pd-NPs/GN/GCE　could　remarkably　decrease　the　overpotential　and　enhance　the　electron-transfer　rate　due　to　the　good　contact　between　Pd-NPs　and　GN　sheets,　and　Pd-NPs　have　high　catalytical　effect　for　H　2　O　2　reduction.　Amperometric　measurements　allow　observation　of　the　electrochemical　reduction　of　H　2　O　2　at　0.5V　(vs.　Ag/AgCl).　The　H　2　O　2　reduction　current　is　linear　to　its　concentration　in　the　range　from　1×10　-9　to　2×10　-3　M,　and　the　detection　limit　was　found　to　be　2×10　-10　M　(S/N=3).　The　as-prepared　nonenzymatic　H　2　O　2　sensor　exhibits　excellent　repeatability,　selectivity　and　long-term　stability.　©　2014　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim.