Abstract: Based on the observed monthly precipitation data at 6 stations in Dalian from 1964 to 2016,the NCEP/NCAR monthly mean reanalysis data during 1948-2016 and the circulation feature data of the western Pacific subtropical high (WPSH) given by the National Climate Center,the characteristics of the atmospheric circulation anomalies of the extremely drought/flood occurrences from July to August were studied using the methods of composite analysis and correlation analysis.Meanwhile,the causes of midsummer drought and waterlogging were revealed by considering atmospheric circulation anomalies.The results show that in midsummer waterlogging (drought) years in Dalian area,the northeast China westerly jet at 200 hPa is stronger (weaker) and the Yangtze River Valley westerly jet is weaker (stronger).At the same time,the location of the Western Pacific Subtropical high ridge line is more-northward (more-southward) and that of the East Asia trough is more-westward (more-eastward) at 500 hPa as well as the south wind anomalies at 850hPa is stronger (weaker).In addition,the anomalous ascending (descending) motions occur in the meridional circulation of vertical speed along the longitude of Dalian,which results in midsummer precipitation anomalously increasing (decreasing) over Dalian area.