Polyoxometalates (POMs ) are novel and unique inorganic building blocks, which can activate the terminal oxygen or bridging oxygen by adjusting the synthesis conditions, thus obtaining various compounds. In order to study the electroche-mical properties of POMs, Keggin-phosphomolybdic acid and 1,4-bis ( imidazolyl ) butane (L) are selected to synthesize a new inorganic-organic hybrid compound (H₂L)₃(PMo₁₂O₄₀)₂ based on polyoxometalates by hydrothermal method. The electrocatalysis activity of the compound to nitrite is studied.The compound has been characterized by elemental analyses, IR, TG, X-ray single crystal diffractions and PXRD, and the connection between synthesis conditions(for example pH values) and compound structures is also studied. The electrochemical behavior and electro-catalysis of the target compound are studied. Single-crystal X-ray diffraction analysis reveals that the polyoxometalates and the organic donor are linked to become 3D structure by hydrogen bonds (triclini, P-1). And Fluorescence analysis indicates that the fluorescence of the compound mainly comes from ligand contribution. The compound exhibits remarkable catalytic activity to nitrite ions and may be actually used for the detection of nitrite.