Photocatalytic reaction for synthesizing methacrolein from C3H8 and CO2 on semiconductors has a great significance in utilization of alkanes and protection of environment. Solid material of metal-decorated coupled semiconductors Cu/V2O5-TiO2/SiO2, prepared by chemical modification method and the isovolumetric impregnation method, was introduced into photo-stimulated surface reaction (PSSR) process to synthesize methacrolein from propane and carbon dioxide. BET, XRD, TEM， IR, Raman and UV-VIS DRS techniques were used to characterize the surface structure, photon absorbing and chemisorbing ability of the material. It was shown that the active species of the photocatalyst Cu/V2O5-TiO2/SiO2, are dispersed well on the surface of the support: the extremely small particles of V2O5, and TiO2 crystallites exist on the surface of SiO2, while the metal Cu is then highly dispersed in the surface of these semiconductors. Another distinct characterization of these materials on their surface structures is that the semiconductor V2O5 is coupled with TiO2 by V—O—Ti bonds. They also form the chemical bonds with silica, which increase the combination of active species and the support. In addition, there exist abundant active sites on the surfaces of the three photocatalysts such as metallic site Cu, Lewis acid sites Tin+ or Vn+ and Lewis base sites M=O or V—O—Ti. The modification to metal Cu is helpful to expend the light-responding scope of the material, which also can improve the photo absorbing ability of the whole reaction. The active chemisorbing of CO2 and propane on the catalyst greatly promotes the photochemical synthesis of methactolein, even in low temperature. Based on the experiments, the mechanism of photo-stimulated surface reaction for synthesizing methacrolein from C3H8 and CO2 on Cu/V2O5-TiO2/SiO2 was proposed.