SnO2 doped with rare earth Sm, containing different amount of oxygen vacancies, was prepared by hydrogen reduction method, and characterized by means of X-ray diffraction XRD. and X-ray photoelectron spectroscopy XPS.. The study of gas-sensing properties of the sample was carried out. The tested gas was n-C6H14, H2, C2H5OH, C6H6 and CO, respectively. Experimental results showed that the specific surface area of sample increases with the amount of oxygen vacancies, and the gas-sensing properties of SmrSnO2 vary with the amount of oxygen vacancies, therefore, it is possible to improve gas-sensing properties of doped SnO2 by controlling its oxygen vacancy.