A novel strategy for selective and sensitive amperometric detection of lead ion (Pb(2+)) was proposed based on target-induced strand release. The underlying gold electrode was pre-modified with dendritic gold nanoparticles by direct electrodeposition to afford increased electrode surface area for immobilization of thiol group-containing capture DNA molecules. The hybridization of the capture DNA molecules with Pb(2+)-specific aptamer molecules to form a DNA duplex, into which methylene blue was intercalated, induced measurable electrochemical signal. Upon addition of Pb(2+), it could specifically bind to its aptamer to form Pb(2+)-stablized G-quadruplex and induce the aptamer strand to release from the electrode surface into solution, accompanied by the release of intercalated MB responsible for significant signal reduction. The fabricated biosensor showed a linear response to the logarithm of Pb(2+) concentration over the range of 1.0 × 10(-10) M to 1.0 × 10(-7) M with a detection limit of 7.5 × 10(-11) M. In addition, this strategy afforded an exquisite selectivity for Pb(2+) against other metal ions. The excellent sensitivity and selectivity show good potential for Pb(2+) detection in real environmental samples.