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Tin oxide nanowires were successful prepared using thermal evaporation method. The crystal structure and surface morphology of the nanowires were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. The as-prepared nanowires are rutile single crystal SnO₂ structure, with diameter in 50-200nm, and length of 5-15μm, conforming to the gas-liquid-solid growth mechanism. The heater structure gas sensor was prepared using SnO₂ nanowires as the gas sensitive material. The gas sensitive performance of the samples was tested in ethanol gas concentration range of 25×10^-6-500×10^-6. The results show that the best working temperature of the sensor is about 260℃; in the 25×10^-6 and 500×10^-6 ethanol gas environment, the sensitivity is 7.54 and 111.01 respectively, response time of the sensor is 2-20s, and recovery time is 5-33s;the sensitivity and the gas concentration has a good linear relationship within the measuring range; the sensor has favourable stability with less than 5% repeated measurement error in 7 days.