Ethyl S-diisopropylaminoethyl methylphosphonothioate (VX) in aqueous phase was decomposed by Ag- and Au-TiO2 photocatalyst. Photocatalytic decomposition rate, r(VX), was accelerated in the order of Ag-TiO2 > Au-TiO2 > bare TiO2 as a consequence of improving charge separation and increasing partial decomposition of VX molecular structure. It was suggested that the photocatalytic decomposition of VX molecule at the Au- and Ag-TiO2 was carried out by C-N, P-S cleavage and oxygenation.