Abstract: In this paper, doped α-Fe₂O₃ nano-powders were prepared by coprecipitation, citrate complex decomposition and urea hydrolization. The results measured by X-ray diffraction (XRD), transmission electron microscope(TEM), specific surface area(BET) and their gas sensor reveals that the powders within 10～40 nm can be prepared under controlling appropriate factors, the powders made by co-precipitation have smaller particle and higher sensitivity and their gas sensors have higher sensitivity and higher CO selectiveity.