Based on the surface ozone observation data from 222 cities of 20 provinces in eastern China and the global reanalysis wind data from 2015 and 2019,this paper investigated the spatial-temporal distribution characteristics of ozone in eastern China and evaluated the influence of ozone photochemical transport in the upwind on seasonal variation of ozone mass concentration in the downwind under the background of Asian summer monsoon (ASM).Results show that the ozone mass concentration in eastern China is higher in summer and lower in winter,and increases in the order of Southeast,East,Northeast and North China.The ozone mass concentration in North China and Northeast China at middle and high latitudes is significantly higher than that in East China and South China at middle and low latitudes.Diurnal variations of ozone mass concentration exhibit similar single-period patterns that remain low at night,gradually increasing in the morning and reaching peak during afternoon and twilight in different cities and seasons,showing typical photochemical controlling characteristics.In spring,ASM starts to influence eastern China and causes a large area of high ozone mass concentration in East,North and Northeast China.In summer,ASM continuously transports and accumulates ozone and its precursors from South China and East China with lower latitude to North China and Northeast China with higher latitude,and photochemical reaction occurs under the action of summer strong ultraviolet radiation,leading to summer ozone pollution in North China and Northeast China.