Abstract: Using observation and reanalysis data, this study explores main atmospheric circulation anomalies and external atmospheric forcing factors that affect summer ozone concentration variations in China during 2013–2020. The results show that the dominant mode of summer ozone concentration variations in China is characterized by the same anomalies over the whole region, with the most significant changes occurring in central and eastern China. Circulation anomalies related to an increased summer ozone concentration in China are mainly featured by low-level cyclonic circulation and low-pressure anomalies in the Northwest Pacific region. This circulation can weaken the transport of climatological water vapor, reduce the specific humidity of atmospheric water vapor, and thus increase the near-surface ozone concentration by enhancing solar radiation and suppressing the moisture removal effect. Further analysis indicates that the external forcing factors that significantly affect changes in the summer ozone concentration in China and the corresponding atmospheric circulation anomalies are mainly derived from the component mode of summer SST anomalies over the maritime continent. These anomalies can modulate local circulation and then affect the summer ozone concentration anomaly in China by adjusting the cross-equatorial Hadley circulation anomaly. Maritime Continent SST anomalies exhibit strong persistence and are significantly correlated with the subsequent summer ozone concentration in China two months in advance. Therefore, we can use the maritime continent SST anomalies to conduct predictability research on changes in the summer ozone concentration in China.