Reducing the sensing temperature of semiconductor oxides to room temperature has been actively pursued recently. In present work, the TiO2 gas sensing thin film was prepared on the alumina substrate by a sol-gel method, in which the major raw materials were the tetrabutylorthotitanate （Ti（OBu）4） and ethanolamine （EA）, while the main additive was polyvinyl pyrrolidone （PVP）. The TiO2 thin film showed a strong oxygen-response under visible light at room temperature, when only PVP was the additive in the sol-gel solution. The oxygen-response of the TiO2 thin film was weak if both PVP and citric acid （CA） were added into sol-gel or without PVP. It was found that the TiO2 thin film was porous when only PVP was added into the sol-gel and the thin film was continuous and compact when both PVP and CA were added or without PVP. The effects of the porous structure and light were discussed, and the future directions were suggested for further improving the gas sensing properties of TiO2 thin films.