Abstract: Theory calculation for band structure of TiO₂-based gas-sensing materials and the orbital energy level of tested gas molecules were carried out.The best operating temperatures of TiO₂-SnO₂ gas sensor to some gases were measured experimentally.The results show that there are some new energy bands in the band gap and the conductance band move towards lower energy state.These effects are beneficial to the electron excitated.When the operating temperature at 260℃,the resistance of TiO₂-based gas sensor is 22.5MΩ,while for the non-doped TiO₂ gas sensor is 44.5MΩ.When the lowest unoccupied orbital energies（ELUMO） of the tested gas decreased,the operating temperature of gas sensors dropped and the sensitivity increased as the reaction activation energy decreased.