Abstract: The spatio-temporal variation characteristics of ozone concentration in the three major urban agglomerations of Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta in China from 2015 to 2020 were analyzed, and the main factors affecting temporal and spatial changes were studied based on random forest model and geographical detector model. The results showed that: 1) From 2015 to 2020, the temporal and spatial evolution characteristics of ozone concentration values of the three urban agglomerations showed an increasing trend year by year, and the ozone variation rate showed a trend of "decreasing from the central to the south": Yangtze River Delta (3.4%) > Beijing-Tianjin-Hebei (2.9%) > Pearl River Delta (2.1%). The spatial variation characteristics of the average ozone concentration were "high in the north and low in the south": Beijing-Tianjin-Hebei (98.3 μg/m³) > Yangtze River Delta (96.7 μg/m³) > Pearl River Delta (90.5 μg/m³). 2) Temperature, wind speed, GDP, and energy consumption were not only the main factors affecting the temporal variation of ozone in the three urban agglomerations, but also had a threshold effect on ozone concentration. 3) Energy consumption and GDP were the main factors affecting the spatial change of ozone concentration in the three urban agglomerations, and their interpretation rates were more than 36%. Therefore, for ozone prevention and control in urban agglomerations more attention should be paid to economically developed areas, and key monitoring and early warning should be carried out in high energy consuming areas to achieve the effectiveness of ozone prevention and control in urban agglomerations.