Coordination reaction is a usual way for the concentration of metal ions in aqueous solution. In this work, 5-(5-iodine-2-pyridine azo)-2,2 amie toluene (5-PADAT) was firstly casting onto carbon glass electrode (GCE), play a role of ‘bait’; then, immersed 5-PADAT modified GCE into immersed aqueous solution containing order of magnitude ppm Palladium ions (Pd2+, play a role of ‘fishes’); ‘Fishes’ were captured by ‘bait’ with the reaction process of 5-PADAT and Pd2+, leading to the concentration of Pd2+ onto the GCE; Cyclic voltammetry was employed to reduce Pd2+ in situ, formed Pd nanoparticles (PdNPs) modified GCE. It can be used to detect the oxidation of hydrazine hydrate at a very low potential, 0.1 V.