Abstract: <FONT face=Verdana>There are always some disadvantages,such as impurity ions and low selectivity of SnO2-based gas sensors etc.of SnO2 prepared by conventional processes.In order to improve those disadvantages,a new SnO2 preparation method was put forward.Method used Sn powder as raw material and took advantage of characteristic of Sn dissolving in hot oxalic acid to synthesize SnO2 via dissolution-pyrolysis process.Product′s phase structure and morphology were characterized by XRD and SEM etc..Results showed that prepared SnO2 belonged to tetragonal structure;morphology of the powder calcined at 700 ℃ was multilayer of large flake;when the temperature was 800 ℃,it was half-curled sheet;and it became cauliflower-]like calcined at 900 ℃.Gas sensitivity properties of gas sensors prepared by SnO2 were also measured.Results indicated that the gas sensors which were calcined at 800 ℃,had a sensitivity to Cl2 with volume fraction of 1×10-4as high as 127 at the working temperature of 225 ℃ and the sensitivity to Cl2 with volume fraction of 1×10-5still reached 7.Moreover,those sensors based on SnO2 also had satisfactory selectivity and quickly response-recover time. </FONT>