The meteorological causes of the severe flooding of the Changjiang during June-August in 1998 is analyzed by using GMST_BB data.The results show that under the abnormal general circulation caused by ENSO event and the early days heavy snow over the Tibetan Plateau,the floods was caused by the four persistent torrential rainfall processes associated with strong subtropical high lying to west and south of normal position,and weak ITCZ and summer monsoon and frequent interaction between cold air from the mid latitudes and warmer air from the tropics.