The invention relates to a method for producing a polypyrrole-coated nickel cobaltate nano wire array graphene electrode and an application of the graphene electrode for detecting heavy metallic lead ion. A hydro-thermal kettle is used for performing a hydro-thermal reaction of graphene oxide to obtain the 3D graphene electrode having a three dimensional structure, a secondary hydro-thermal process is used, and a NiCo2O4 nano wire array is grown on the surface of the 3D graphene electrode. A layer of ultrathin conductive polymer polypyrrole layer is coated on the surface of the NiCo2O4 nano wire array by using a chemical gaseous polymerization method; and the polypyrrole-coated NiCo2O4nano wire array graphene electrode is finally obtained. The electrode is used for detecting heavy metal Pb<2+>. According to the invention, the sensitivity of a sensor constructed based on NiCo2O4-coated PPy/3D graphene is 115.621[mu]A [mu]M<-1>, linearity scope is 0.0125to 0.709 [mu]M, and the lowest detection limit is 0.2 nM, and the sensor has good interference immunity and stability.