It was previously reported that CO2 could be reformed into CO, CH4, etc., which can be used as fuels, by TiO2 as the photocatalyst and under UV radiation. If this technique could be applied practically, a carbon circulation system would then be able to be constructed by reforming CO2 from combustion, using solar energy, to fuel, which would solve the problem of global warming and fossil fuels depletion all together. However, the technology is not yet practicable as the fuel concentration of products is too low. To increase the concentration and improve Cot reforming performance on TiO2, a membrane reactor composed of TiO2 and gas separation membrane prepared by sol-gel and dip-coating method has been built. Study on the factors influencing membrane performance, e.g. rising speed in the dip-coating process, has been carried out with the reactor. The results of the study are reported in this paper. (C) 2009 Elsevier B.V. All rights reserved.