Abstract: The development of science and technology and the continuous improvement of productivity have brought great convenience to people’s lives. At the same time, due to energy consumption and the generation of additional pollutants, the environment is facing huge challenges Among them, air pollution is one of our main concerns. As a major air pollutant, NO₂ poses a great threat to water bodies, soil and atmosphere, such as surface water, soil acidification and photochemical smog, etc.. Meanwhile, it is also harm to human health, for example respiratory diseases, cardiovascular and cerebrovascular diseases. Therefore, it is essential to prepare a portable gas sensor that is suitable for environmental monitoring and has low operating temperature, detection limit and high sensitivity to determine the NO₂ in the environment. This article summarizes the research progress of several typical N-type semiconductor metal oxide NO₂ gas sensors, and prospects the application of NO₂ sensors in environmental monitoring and the future research directions.