A multilayer composite film of the 12-tungstophosphate H-3[PW12O40](3-) (PM12) and cadmium oxide nanoparticles (CdO) was fabricated on quartz and silicon by the layer-by-layer (LBL) self-assembly method. The film was characterized by UV-vis spectroscopy, atomic force microscopy (AFM) and luminescence spectra. The proposed composite film exhibits higher photocatalytic activity toward methyl orange (MO) solution at pH 3.5, compared to single PW12 and CdO films. The degradation rate was affected by initial concentration of PW12, pH value of MO solution, inorganic ions concentration and type in MO solution. In addition, the composite film displays luminescent property and reversible electrochromic property with fast response time. (C) 2014 Elsevier B.V. All rights reserved.