SnO2/CuO/polymer flexible thin films were prepared by a solution casting technology and characterized by high-resolution TEM and XRD. The influences of key operational parameters on photocatalytic decolorization of azo dye (Biebrich Scarlet Red, BSR) were investigated systematically. The results showed good crystalline and clear lattice spacings of the novel composite photocatalyst. BSR was bleached effectively and the decolorization efficiency was >98 % in the presence of 1.0 g L-1 photocatalyst under simulated solar light irradiation. The decolorization was more effective in acidic solution with the optimal pH in the range of 4-6. The tested co-anions in general decreased the decolorization rates by decreasing the adsorption of BSR on the surface of the photocatalyst and reacting with positive hole (h(+))/hydroxyl radicals (HO.).