Based on monitoring data of atmospheric pollutants in Nanjing from Jan.1,2015 to Feb.10,2021,the spatial-temporal distribution characteristics of Nanjing's ambient air quality and the contribution of potential source areas were analyzed.The average concentrations of six air pollutants (CO,NO₂,SO₂,O₃,PM₁₀,and PM_2.5) were 800 μg·m^-3,43.1 μg·m^-3,13.0 μg·m^-3,106.0 μg·m^-3,77.1 μg·m^-3,and 43.0 μg·m^-3,respectively.The average concentration of ozone in Nanjing was higher than that in China's other typical cities (Beijing,Shanghai,Guangzhou,Chengdu,Lanzhou,and Wuhan).The number of pollution days for NO₂,PM₁₀,and PM_2.5 were reduced by 29.1%,38.1%,and 28.1% during 2015 to 2020.However,the frequency of ozone pollution days was increasing (the highest value in summer and the lowest value in winter).The potential source analysis of fine particulate matter in January of 2015-2020 was carried out.It was found that the potential source for Nanjing's PM_2.5 was surrounding industrial areas (Anhui province,north of Jiangsu province,and Shandong province).The concentration of air pollutants in Nanjing in 2020 was lower than that in 2019 and 2021.It indicated that the reduction of human activity caused by COVID-19 pandemic has resulted in less air pollutant emissions and improved air quality in Nanjing.