A supramolecular compound composed of reduced phosphopolybdate and FeII was synthesized by hydrothermal method with sodium molybdate, ferric nitrate, phosphoric acid and triethylenetetramine as raw materials. The chemical formula of the compound is ［C8H24N4］1.5［C6H22N4］1.5{Fe［Mo6O12(OH)3(PO4)3(HPO4)］2}·5H2O (1). Single crystal X-ray diffraction, powder X-ray diffraction (PXRD) and infrared spectroscopy (FT-IR) characterizations show that compound 1 is composed of {Fe［P4MoV6O31］2}22- (denoted by {Fe(P4Mo6)2}), protomated triethyltetramine and protomated N, N′-bis(aminoethyl)-piperazine in a three-dimensional supramolecular structure through hydrogen bond interactions. The results of electrocatalytic performance measurement show that compound 1 has good electrochemical sensing performance and low limit of detection (LOD) for chromium ion (CrⅥ), iron ion (FeⅢ), potassium bromate (KBrO3) and ascorbic acid (AA).