Circulation characteristics associated with abnormal rich precipitation in and to the south of Yangtze River basin in summer of 1999 were discussed.The following circulation characteristicswere noticed:During the sustained stage of La Niña period,the intensity of WestPacific subtropical high(WPSH) was below normal with its position more moving northward and eastward.The tropical monsoon over South China Sea was stronger in earlier summer,but weaker later.In upper troposphere,South Asia anticyclone ridge and TUTT located something south.Meanwhile,in lower troposphere,the enhanced transportation of water vapor was formed by the cyclonic abnormal circulation over mid-to low-reach of Yangtze River and to the south of Yangtze river valley.In the summer,the continental high persisted in the mid latitude region of Asia.Mid-and low-latitude circulation anomalies synthetically cause the flooding around and to the south of Yangtze river basin.