Abstract: On the basis of studying the monthly rainfall data and the NCEP/NCAR reanalysis data,the sea temperature data provided by NOAA and 126 circulation indexes provided by the National Climate Center (NCC) that combined with a long-cycle drought-flood abrupt alternation index,the relationships between timely changing characteristics of Chongqings drought-flood abrupt alternation and the atmospheric circulation anomalies during the same period and prophase have been analyzed in this paper.The results are as followsthe summer drought-flood abrupt alternation events in Chongqing have the characteristics of both phase continuity and intermittent coexist,displaying huge annual differences,and the flood-to-drought situation is worse than the drought-to-flood situation.By comparing the drought period of the drought- to-flood years with the flood period of the flood-to-drought years,weve found that the western Pacific subtropical high is abnormally westward,also stronger and wider than before,which will lead to a stronger lower vertical sinking movement and the lack of water vapor transportation from the South China Sea and the western Pacific Ocean,so Chongqing is likely be at the water vapor transporting divergence area,which will lead to little rainfall and will result in drought.By comparing the flood period of the drought- to-flood years with the drought period of the flood-to-drought years,weve also found the trough of west coast of Europe is stronger and the polar vortex is weaker,the western Pacific subtropical high is abnormally westward and stronger,which will lead to a stronger lower vertical sinking movement and a strong water vapor transportation from the south China sea and the western Pacific Ocean,then Chongqing is likely to be at the water vapor transporting divergence area,which results in vast precipitation and floods.The seasonal abnormal oscillation of western Pacific subtropical high might be the major reason for the drought-flood abrupt alternation in Chongqing.The early PDO in March and April together with the sea temperature index of the west wind drift area can be used as a warning signal for Chongqings drought-flood abrupt alternation prediction,which will lead to drought-flood abrupt alternation events when the early PDO in March and April is stronger and the sea temperature index of the west wind drift area is weaker.