A　novel　electrochemiluminescence　(ECL)　biosensor　based　on　CdSe@CdS　quantum　dots　(QDs)　functionalized　MoS2　modified　electrode　was　developed　for　sensitive　detection　of　Pb(II)　using　HRP-mimicking　DNAzyme　biocatalytic　precipitation　(BCP)　for　ECL　signal　quenching.　Polycationic　poly(diallyldimethylammonium　chloride)　(PDDA)　and　negatively　charged　QDs　were　adsorbed　on　the　surface　of　MoS2,　in　sequence,　to　form　the　MoS2-QDs　composites,　which　were　employed　as　a　matrix　for　the　immobilization　of　the　G-rich　DNA　strand,　i.e.,　T30695.　The　MoS2-QDs　were　characterized　by　UV-vis　absorption　spectroscopy,　fluorescence　spectroscopy,　energy　dispersive　spectrometry,　transmission　electron　microscopy,　and　field　emission　scanning　electron　microscopy.　CdSe@CdS　QDs　can　produce　an　ECL　signal　using　0.1　M　K2S2O8　as　a　co-reactant.　T30695　can　combine　with　Pb(II)　ions　to　form　a　stable　parallel　G-quadruplex.　The　G-quadruplex　can　further　combine　with　hemin　to　form　DNAzyme,　which　can　catalyze　H2O2　and　oxidize　4-chloro-1-naphthol　(4-CN)　to　produce　an　insoluble　precipitation　of　benzo-4-chlorohexadienone　on　the　surface　of　the　sensor.　When　the　concentration　of　Pb(II)　in　the　solution　was　increased,　more　of　DNAzyme　was　generated　and　subsequently　more　4-CN　molecules　were　oxidized　catalytically,　leading　to　a　decrease　of　the　ECL　signal.　Using　this　quenching　strategy,　the　ECL　signal　of　the　biosensor　was　linearly　dependent　on　the　logarithm　of　the　Pb(II)　concentration　ranging　from　1.0　x　10(-15)　to　1.0　x　10(-11)　M　with　a　detection　limit　of　0.98　f　M.　The　stability　and　selectivity　of　the　sensor　were　also　investigated.　The　sensor　was　applied　in　the　determination　of　Pb(II)　in　the　real　water　samples　and　satisfactory　results　were　obtained.