A large-scale forest fire occurred in Australia in 2019-2020, which burned more than 8 million hectares of eucalyptus forest in six months. In this work, the variation of NO2 during the Australian fire was studied by the environmental trace gases monitoring instrument (EMI). It was found that in November 2019, the NO2 concentration and distribution in southeastern Australia showed a significant increase compared with the same period in previous years. In addition, aiming at the fires in Australia′s two major national parks, the correlation between the frequency distribution of NO2 relative concentration and the degree as well as frequency of fires was studied. It was found that the frequency distribution of NO2 relative concentration in the two places also increased significantly in November 2019, indicating that forest fire is the main reason for the increase of NO2 concentration in these regions. At the same time, this work also proves the feasibility of EMI in monitoring major pollution events.