Dawson heteropolyacid, H 6 [P 2 W 18 O 62 ], was chemically anchored to the amine-functionalized nanosilica surface in different loadings. The synthesized nanocomposite was characterized by FT-IR spectroscopy and N 2 adsorption experiments. The preservation of the structure of the Dawson and dispersion of the cluster on the support were verified on the basis of the spectroscopic data. The photocatalytic degradation efficiency of the synthesized nanocomposites was studied using an aqueous solution of malachite green dye as a model water pollutant. The mineralization of dye contents was investigated in different loadings from 10 to 30 % at room temperature. Decolorization was observed in shorter time using 30 % loading. The photocatalyst was reusable after the filtration and remained active even after being washed with hot water, which confirm its attachment firmly to the surface of amine-functionalized nanosilica.