In　this　work,　a　sensitive　and　specific　electrochemical　biosensor　for　lead　ion　(Pb2+)　detection　was　developed　by　coupling　with　synergetic　catalysis　of　porous　Au-Pd　bimetallic　nanoparticles　and　hemin/G-quadruplex-based　DNAzyme.　In　the　presence　of　target　Pb2+,　the　substrate　strand　was　cleaved　and　the　enzyme　strand　was　released.　Subsequently,　G-rich　DNA-labeled　Au-Pd　bimetallic　nanoparticle　was　linked　with　the　released　enzyme　strand　through　the　helper　DNA.　Upon　addition　of　hemin,　a　large　number　of　hemin/G-quadruplex-based　DNAzyme　molecules　were　formed　on　the　electrode　to　serve　as　nicotinamide　adenine　dinucleotide　hydrogen　(NADH)　oxidase　and　peroxidase　mimics.　DNAzyme　could　catalyzed　the　reduction　of　H2O2,　generated　from　NADH　in　the　presence　of　O2,　to　produce　an　electrochemical　signal　when　using　thionine　as　the　electron　mediator.　Introduction　of　porors　Au-Pd　bimetallic　nanoparticles　could　enhance　the　detectable　signal　and　cause　the　increase　in　the　sensitivity.　Experimental　results　showed　that　the　variations　(ÎI)　in　the　cathodic　peak　currents　of　the　biosensor　were　linearly　dependent　on　target　Pb2+　concentrations　from　1.0pM　to　100nM　with　a　detection　limit　(LOD)　of　0.34pM.　The　excellent　performance　of　the　sensing　platform　indicated　its　promising　prospect　as　a　valuable　tool　for　simple　and　cost-effective　Pb2+　detection　in　practical　application.　©　2015　Elsevier　B.V.