Pure In2O3 NBs and Er-In2O3 NBs have been successfully synthesized by carbon thermal reduction. The doping of Er leads the optimal temperature of the In2O3 to decrease. The response of the Er-In2O3 sensor to 100ppm of alcohol is 4.8 at 220°C, which is twice larger than that of the pure In2O3 sensor. It is also found that the doping of Er has increased the performance of the sensors. Moreover, Er-In2O3 sensor has a fast response (recovery) time to different concentration of alcohol at 220°C. In addition, the mechanism of pure In2O3 sensor and Er-In2O3 sensor are discussed.