Abstract: Metal-ion doped TiO₂ oxygen gas sensors are introduced briefly, particularly on the history of development and application, and characteristics of metal-ion doped TiO₂.The several problems are focussed on the series of oxygen-sensing mechanism, preparation methods and properties of sensors. In this paper, the relationship between synthesis, microstructure and oxygen-sensing characteristics is discussed.And based on it, some suggestions on the further research and development of metal-ion doped TiO₂ oxygen gas sensors are proposed.