Abstract: In view of the features of torrential rains,an extended forecast of them is of urgent necessity for the flood-protection and construction of the Main Dam on the Three Gorges of the Yangtze River. Hence,studies are concentrated first on the heavy rains that may cause flash-floods,in which a new concept and its mathe-matical expression of "Flood-Causing Torrential Rain" (FCTR)is proposed. Through a series of combination of meteorological and hydrological studies including:climatological and atmospheric synoptic patterns of FCTR,satellite cloud systerns and OLR features,extra-long and long wave fluctuations,low frequencies of atmospheric oscillations,medium-range atmo-physical parameter diagnoses,and relationships between intense rainfall process and flash-flooding,etc,some extended FCTR forecast methods have been established and used experimentally.