Cadmium (II) sensing utilizing three-dimensional graphene/polypyrrole oxides was applied and evaluated for the environmentally relevant analytes. Driven by the need to detect trace Cd (II), we prepared a porous graphene oxide-polypyrrole (pGO/PPy) polymer nanocomposite modified sensor for electrochemical trace analysis of Cd (II). The pGO/PPy was prepared by polypyrrole wrapped with graphene oxide using ultrasound-assisted polymerization and graphene oxide functionalized with carboxyl, which was modified on the sensing electrode for pre-concentration and enhanced the absorption of heavy metal ions. Three-dimension graphene oxide and interconnected porous structure of polypyrrole were fabricated by electro-polymerization and sonication to enhance the pre-concentration factors and the sensitivity for cadmium determination. The cadmium sensor fabricated with pGO/PPy nanocomposite displayed a displayed a considerable sensitivity within the linear range from 1 mu g.L-1 to 100 mu g.L-1, a detection limit of 0.05 mu g.L-1 2-orders-lower cadmium than the WHO standard limit. The cadmium sensor could be applied in tap, pond and river water with a high selectivity minimizing electroactive, interfering ions. (C) 2019 The Electrochemical Society.