Surface modification on WO₃ was carried out by loading KOH, NaOH and CsOH to study the influence of surface interactions on photocatalytic activity of this material. Photodegradation of 2-propanol, methanol, ethanol, acetone and propane in gas phase under visible light irradiation shows loading of KOH, NaOH and CsOH on WO₃ enhanced the photodegradation rate about 4 and 3 times respectively. Loading of KOH on TiO₂ were carried out for comparison and the results showed enhancement of photoactivity by KOH loading for WO₃ which was much higher than that of TiO₂. Increasing the rate of the photocatalytic reaction is attributed to compensation of the high tendency of WO₃ for H⁺ donation and making multi-electron O₂ reduction by loading of KOH on the surface.