The characters of inter-annual and inter-decadal variations of summer precipitation over the mid-and low-reaches of Yangtze River have been statistically analyzed from 1951 to 2002.Results indicate that the 1960's and 1970's are dry-spells and the 1990's a wet-spell,and the 1980's is a transition period of drought alternating with flood.Drought and flood are determined by the polarities of the inter-annual and inter-decadal changes.On this basis,simultaneous temporal and time-lagged realtions of the composite latent heat and sensible heat flux anomalies with the atmospheric circulation anomalies on the inter-annual and inter-decadal scales are analyzed.Results show that the heat flux anomalous mode in the T and R areas in the preceding spring is a presage for the summer rain anomaly in the mid-and low-reaches of Yangtze River.