In order to study the characteristics of air quality changes and their influencing factors in Urumqi,China, during the strict prevention and control of COVID-19, the data of hourly air quality index (AQI), particulate pollutants (PM_2.5, PM₁₀) and gaseous pollutants (SO₂, NO₂, CO, O₃) during the two strict epidemic prevention and control periods (January 26 to March 21, 2020 and July 20 to August 29, 2020) as well as before and after the two control periods in Urumqi in 2020, and in the same period of 2019, were selected for comparative analysis, the contribution of gaseous pollutants to the secondary synthesis of particulate matter was explored, and the quantitative detection of the factors affecting air quality was carried out using geographical detectors. The results show that compared with the same period in 2019, during the two epidemic prevention and control periods in Urumqi in 2020, PM_2.5, PM₁₀, SO₂, NO₂ and CO concentrations all show a downward trend, with a decrease of 36%, 55%, 10%, 18% and 49%, respectively. While compared with the two strict epidemic prevention and control periods, the AQI, particulate matter concentration and gaseous pollutant concentration in the pre and post epidemic periods of 2020, are generally higher. That indicates that the epidemic prevention and control measures acquired have reduced the concentration of particulate pollutants and gas pollution in Urumqi to some extent, leading to the improvement of the air quality. The single factor detection results show that CO and PM_2.5 are the dominant factors in air pollution indicators, and the temperature has a relatively significant effect on air quality in meteorological factors. The interaction factor detection results show that air pollutants PM_2.5 and PM₁₀ have the most obvious effects on AQI under the interaction of the other factors, and the interaction of relative humidity with other factors in meteorological factors has a significant effect on AQI. So it is shown that the air quality of Urumqi city is the result of the interaction of multiple factors. This study provides a theoretical basis for the improvement of air quality and air pollution prevention and control in Urumqi.