Abstract: This study presents the spatio-temporal differentiation of ozone concentration and its driving factors in the Yangtze River Delta urban agglomeration from 2015 to 2017 via Kriging interpolation, spatial auto-correlation, hot and cool spot analysis, and geographical detection. The results show that: 1) the concentration of ozone rises during this period with 90th percentile of maximum daily 8-h average ozone concentration rising from 149 μg/m3 to 166 μg/m3, the percentage of days which exceed standard (GB 3095-2012) going up from 9.3% to 12.1%, and the proportion of days with ozone as primary pollutant to total polluted days increasing from 32.3% to 46.4%; 2) impacted by the large inter-annual fluctuations of temperature and precipitation, the curves of monthly ozone concentration differ slightly in different years; the days with over-limit ozone concentration mainly occurred from April to September, which account for 88.3%, 98.2% and 97.0% of the year 2015, 2016 and 2017, respectively; 3) due to the rapid increase of ozone concentration in Anhui province, the spatial distribution pattern of ozone concentration evolves from high in East and low in West to high in North and low in South, but the concentration is more homogenized than before; 4) with the rise of ozone concentration, the hot spots expand from Taihu Lake area to Nanjing metropolitan area, while the cool spots shrink evidently in Anhui Province; 5) the analysis of geographical detector shows that socioeconomic factors such as economic scale, urbanization and emission source have a significantly positive impact on the spatial distribution of ozone concentration, while precipitation and wind have a negative impact on the spatial distribution of ozone concentration since the precipitation scavenges ozone and wind promotes the dispersion of ozone.