Using the monthly precipitation of 160 stations in China from 1951 to 2000 year,deficit/excessive summer rain years of Changjiang-Huaihe River Basin(the Jianghuai region) are selected.It is found from the composite analysis of 500 hPa geopotential height anomaly that the blocking high near Okhotsk maintains steadily in excessive summer rain years,whereas the high ridge near Okhotsk is weakened in deficit summer years.The EliassenPalm flux are calculated to explore the reason for differences of the 500hPa circulation in middle and high latitudes between deficit and excessive summer rain years of Jianghuai.The analysis results of Eliassen-Palm fluxes indicate that in excessive summer rain years the forcing of transient waves to the mean flow makes patterns of zonal and meridional wind anomalies in favor of the maintenance of Okhotsk blocking high and thus the strengthening of the southward transfer of cold air,and excessive summer rainfall in Jianghuai,whereas in deficit summer rain years,the forcing of transient waves to the mean flow weakens the high ridge near Okhotsk and thus the weaking of the southward transfer of cold air,and deficit summer rainfall in Jianghuai.