Abstract: TiO₂ based nanosized powders doped with Mo⁶⁺ were prepared by sol-gel technique using TiCl₃. It indicates that rutile TiO₂ can be obtained at low annealing temperature（400℃）. Oxygen sensitivity of thick-film sensors were also researched at low operating temperature（145℃） and 1×10^-4oxygen concentration. The sensitivity of TiO₂ doped with Mo⁶⁺ is better than that of pure TiO₂ due to the charge density on surface, which is detected by Zeta potential.