The characteristics of the precipitation over the middle reaches of the Changjiang river are concentrated rainfall and the total rainfall amount is 734.7mm from June to July in 1998.In June,1999,the rainfall amount over the middle reaches of the Changjiang river is 325.5mm,the rainfall amount over the lower reaches of the Changjiang river is 636 2mm.The monthly rainfall amount is maximum in Anqing and Shanghai since 1949.The upper level jet lays in the northeast of South Asia high,the low-level jet lays in the northwest of subtropical Pacific high in middle and lower atmosphere.There is a upward current and a wet tongue associated with vortex and hard rain between the upper-level jet and the low level jet.This is of the characteristics of monsoon stream tube.