N-type semiconducting nanometer oxides including SnO2,In2O3,ZnO,an d Fe2O3 were prepared by solid state reaction with inorganic compounds at room t emperature. The phase composition and microstructure of the powders were studied by XRD and TEM. The results show that the complete solid state reaction was ach ievable at room temperature. The mean particle size of powder is below 100 nm. T he gas sensing characteristics of the pure powders were studied. The results sho w that sensors made from SnO2,In2O3 have a high sensitivity and selectivity to LPG and ethanol, while the sensors made from ZnO,Fe2O3 have relatively poor sen sitivity.