The invention discloses a detection method of heavy
metal lead ions. A ratio fluorescent biological probe is finally formed by modifying nanogold on the surface of an aminated
magnetic bead to form a
fluorescence quenching body, connecting the nanogold to a sulfhydrylated
DNA enzyme through an Au-S bond and modifying red
quantum dots to form a red fluorescent probe, and combining with a substrate chain modified with green
quantum dots at the other end through base complementary
pairing. Under the effect of
DNA, Pb<2+> can recognize and shear the substrate chain, so that a distance between the green
quantum dots and the nanogold is changed, the
quenching and
recovery of green
fluorescence are realized, and finally, the quantitative detection of Pb<2+> is realized through the change of a red-green
fluorescence ratio due to the change of the green
fluorescence intensity. The method has the characteristics of simplicity and convenience, a double-
signal detection mode is adopted, the influence of a background environment on a detection result is effectively reduced, and an experiment error is reduced; the method is simple and feasible to operate, low in detection cost and capable of realizing quantitative detection of a target object through a fluorescence spectrophotometer.