During the COVID-19 pandemic in 2019 and 2021, strong control measures were taken in Xi'an, China, therefore, the impact of different degrees of emission reduction measures on air quality was studied comparatively. In this work, the characteristics of air quality changes during the pandemic period (December 2019-February 2020 and December 2021-February 2022) and the normal production period (December 2020-February 2021) in Xi'an were compared and analyzed by methods of characteristic radar map, spatial interpolation and HYPLIST trajectory model, and the potential causes of air quality change under anthropogenic emission reduction scenarios were discussed. The results show that: (1) The overall spatial distribution of air quality index (AQI) in Xi'an exhibits a characteristic of "inferior in northwest and superior in southeast". In 2020, the air quality of Xi'an city was significantly improved during the strict pandemic control period, with 53% days with the air quality being excellent and good. While in 2022, the air quality was not significantly affected by the strict epidemic control measures. (2) During the strict control period of the epidemic in 2020, except for O₃ the concentrations of other pollutants, decreased significantly, with PM_2.5 (42.90%) > NO₂ (42.13%) > CO (35.37%) > PM₁₀ (32.58%) > SO₂ (17.40%). While in 2022, only SO₂ and NO₂ concentrations decreased, with a decrease of NO₂ (31.86%) > SO₂ (18.31%).The type of pollution during the pandemic was mainly secondary pollution. (3) During the pandemic period, polluted weather was mainly caused by anthropogenic source emissions and regional pollutant transport on the basis of high humidity, calm wind weather conditions and basin topography. Therefore, promoting the coordinated reduction of pollutant emission, as well as joint prevention and control in Guanzhong area, is the key measure to improve air quality.