The temporal and spatial characteristics of the onset of the summer monsoon rainfall and the shift of the rain belt over East China is analysed based on the dekad rainfall data at 41 stations from April to September in 1991. The distribution patterns of the summer monsoon rainfall arediscussed using empirical orthogonal function (EOF) and its 20 to 30 day'low-frequency variability is also discussed. The difference between the rainfall distribution patterns in flood years and that in drought years in the Jianghuai area is considered tentatively.