Abstract: Tin dioxide gas-sensing materials containing different oxygen hole concentration (SnO_2-x) were prepared by reducing Tin dioxide with hydrogen at 160℃. The morphology, average valence of Sn and sixe of crystal grain were determinated by XED, XPS, SEM and specific surface technique. The gas-sensing properties under different gaseous circumstances (n-hexane, hydrogen, ethanol and carbon monoxide) were measured. The relationship between gas sensitivities and the oxygen hole concentration (x value in SnO_2-x) was discussed. The x value could be controled for the purpose of better gas sensitivity and better selectivity.