Herein, ZnO nanoflowers without any doping and modification were synthesized by hydrothermal method. The room temperature nitrogen dioxide sensor with high sensitivity, selectivity and long-term stability was prepared by combining ZnO nanoflowers with interdigital electrodes. The average diameter of the ZnO nanoflowers was about 0.9-1 mu m. In addition, the gas sensing properties of the nitrogen dioxide gas sensors at room temperature were investigated. Compared with other ZnO sensors, the sensor based on the ZnO nanoflowers revealed outstanding sensing response to NO₂, giving a response of 0.05-6 ppm. The sensor exhibited a lower detection limit of 0.05 ppm and had an ultra-high response to 1 ppm NO₂at room temperature. The response was only decreased by 16% of the initial value after 40 days of measurement. The Schottky barrier could be the key factor for the excellent NO2 sensing properties, which was formed between the Au electrodes and ZnO nanoflowers.