The p-Na0.23TiO2/n-TiO2 heterojunction sensor was synthesized via one-step hydrothermal method. The characterization results shown that the special porous nanotube structure was conducive to a high specific surface area, rich oxygen species and smaller the crystallite size. The gas-sensitive test results exhibited that the response value of Na0.23TiO2/TiO2 nanotubes to 10 ppm NOX was 17.3 at room temperature, which was about 7 times higher than that of commercial TiO2 particles at 100 °C. Meanwhile, the sensor shown good long term stability, high selectivity and good humidity resistance. Therefore, we believe that Na0.23TiO2/TiO2 sensors have a potential application value for the detection of NOX.