The electrochemical multilayer films of crown-shaped polyoxomolybdate Na-21 {[Na-5(H2O)(14)]boolean AND[(Mo20Mo26O134)-Mo-V-O-VI(OH)(10)(mu-CH3-COO)(4)]}center dot CH3COONa center dot 90H(2)O (Mo-46) and polyelectrolytes by layer-by-layer assernbly were investigated. The stable multilayer films were assembled by alternate adsorption of negatively charged POM and positively charged polyelectrolytes is from their aqueous dispersions. UV vis spectroscopy and cyclic voltammetry were used to monitor the regular growth of the multilayer films. The multilayer films-modified ITO electrode was used for the detection of electrocatalytic activity toward the reduction of nitrite, bromate, and hydro.-en peroxide. The proposed novel immobilized method exhibited good stability, reproducibility and high sensitivity for the determination of electrocatalytic, which is important for practical application. (c) 2004 Elsevier Inc. All rights reserved.