Abstract: Based on daily regional mean rainfall, persistent drought and flood events that lasted at least 10 days in two inner lakes (Dongting and Boyang)were selected. Using 4 times-daily National Center for Environmental Prediction (NCEP) reanalysis data, these drought and flood events have been preliminarily diagnosed. The results show as follows. (1) The composite standard geopotential height at 500 hPa exhibits an obvious longitudinal wave train from high to low latitude in the eastern Asian-Pacific region, i.e., the “－＋－”and “＋－＋” patterns are dominant over the eastern Asian-Pacific region in the persistent drought and flood events respectively. The developing, persisting and decaying phases in drought and flood events are closely linked with the intensity and location of the subtropical high as well as the mid-high latitude blocking high. (2) Furthermore, East Asian summer monsoon stays in the strong (weak) phase when persistent drought (flood) events happen. The persistent drought events are accompanied with a weak tropical convergent system and a strong subtropical convergent system. In turn, the persistent flood events are accompanied with a strong tropical convergent system and a weak subtropical convergent system. (3) At the same time, the persistent drought and flood events go respectively with the local integral water vapor flux divergence and convergence. As for the altitudinal profile of the water vapor flux, divergence (convergence) in the mid-lower layer and convergence (divergence) in the high layer are very obvious in the drought (flood) events. Both the strongest divergence in droughts and convergence in floods appear at the level of 850 hPa.