In order to reveal the spatio-temporal aggregation pattern of O₃, the observation data of O₃ concentration from 1144 monitoring stations in 338 cities of China was analyzed by using spatial interpolation and spatial self-correlation during 2016 to 2018. The results indicated an overall upward trend of O₃ concentration (90 percentile) in China (from 141.54µg/m³ in 2016 to 153.21µg/m³ in 2018). The O₃ concentration was the highest in densely populated areas such as North China, the middle and lower reaches of the Yangtze River. The spatial distribution of O₃ concentration showed a significant clustering pattern and similarity characteristic. And the clustering and similarity characteristic increased from 2016 to 2018. There was a differentiation from the north to the south of the annual cluster zones, which was presented in the form of the high-value cluster zones in the north while the low-value ones in the south. The high-value cluster zones were located in North China (22.19%~29.59%), while the low-value zones were located in South China (15.98%~22.19%). In addition, seasonally, the cluster pattern of high-value and low-value zones of O₃ concentration showed an evidently periodical clockwise variation. Over the three years, the spring cluster zones were identical to the annual ones. In summer, both high-value zones and low-value zones had gradually expanded towards the west. While in autumn, the cluster pattern differentiated from the east to the west changed by a clockwise-shift, after which the high-value zones (the low-value zones) move toward south (north) gradually by a clockwise-shift. In winter, the cluster zones differentiated from the north to the south, in the pattern of the high-value cluster zones in the south while the low-value ones in the north.