A record-breaking precipitation event happened in Henan Province in July 2021, which caused great casualties and economic losses. This event exposed some deficiencies of precipitation prediction in flood-season in Eastern China. This study applied the ERA5 reanalysis product and a dynamic adjustment (DA) approach to explore the respective contributions of large-scale circulation and local land-atmosphere interaction in this extreme precipitation event. In DA, the 500ha geopotential height constructed circulation analogs were used to separate the effects of large-scale circulation dynamics and local land surface effects on precipitation anomalies in Eastern China from 1979 to 2021. Finally, the contribution of these two effects to the extreme precipitation event is quantified. The main conclusions are as follows: 2011 is the similar year of 500hPa circulation with July 2021, while the corresponding precipitation fields show significant differences from North China to the middle and lower reaches of the Yangtze River. The influence of atmospheric circulation is separated from precipitation anomaly after DA. The correlation analysis shows that the residual component of precipitation anomaly reflects local land-atmosphere feedback. The residual is the main cause of the anomalous heavy precipitation from Jianghuai region to the lower Reaches of the Yangtze River in July 2021. Attribution analysis shows that the residual component is mainly caused by the change of local thermal factors, enhanced evaporation reduces sensible heat flux and increases precipitation by affecting atmospheric relative humidity and boundary layer height. Among them, evaporation is strengthened, sensible heat flux is significantly reduced, and the unstable energy of atmospheric strong convection is increased, and precipitation is increased by influencing atmospheric relative humidity and boundary layer height. Extended to the precipitation evolution process from 1979 to 2021 in July, it is found that the interannual variability of precipitation residual component is very strong, the extreme precipitation anomaly is mainly reflected in the residual component, and the circulation component is relatively stable. The results emphasize the important influence of local thermal effect on summer extreme precipitation. This study shows that taking both the characteristics of large-scale atmospheric circulation and the contribution of local thermal effects into consideration is necessary to improve the prediction of summer precipitation in Eastern China, and the latter is particularly important to the prediction of summer extreme precipitation.