Nitrogen dioxide is one origin of air pollution from fossil fuels with the potential to cause great harm to human health in low concentrations. Therefore, low-cost, low-power-consumption sensors for low-concentration NO₂ detection are essential. Herein, heterojunction by SnO₂ quantum wires, a traditional metal oxide NO₂ sensing material, and Ti₃C₂T_x MXene, a novel type of 2D layered material, was synthesized using a simple solvothermal method for enhancing gas-sensing performance and reducing operating temperature. The operating temperature was reduced to 80 °C, with a best performance of 27.8 and a fast response and recovery time (11 s and 23 s, respectively). The SnO₂ and Ti₃C₂T_x MXene composite exhibits high speed and low detection limit due to the construction of the heterojunction with high conductive Ti₃C₂T_x MXene. The selectivity and stability of gas sensors are carried out. This could enable the realization of fast response, high-sensitivity, and selective NO₂ sensing under low operating temperatures.