It has been found that the photocatalytic activity of TiO2 toward the decomposition of Ip-dichlorobenzene (DCB) aqueous solution can be greatly improved by loading WO3 On the TiO2 surface. In this work, we have investigated the role of WO3 in enhancing the photocatalytic activity of TiO2. The surface structure of WO3/TiO2 was characterized by surface acidity measurements and by surface analysis with XPS and TEM techniques. WO3 covers the surface of TiO2 with monolayer thickness and the WO3/TiO2 particles are better able to disperse than the pure TiO2 suspended in aqueous solution. The role of WO3 in enhancing the photocatalytic activity of TiO2 has been studied by utilizing the photocatalysts prepared in a film form. First, benzene and 2-propanol were used as gas-phase model compounds. WO3/TiO2 demonstrates 3.6-5.9 times the photocatalytic activity of pure TiO2. Second, methylene blue coated on the photocatalysts was applied in the photocatalytic oxidation reaction. WO3/TiO2 presents only 1.4-1.5 times the photocatalytic activity of pure TiO2 in decomposing the coated methylene blue. Based upon these observations, the mechanistic role of WO3 in the photocatalytic oxidation reaction has been suggested.