Abstract: A year was divided, for the Yangtze Delta region, into six natural seasons. Spring Rain, Plum Rain, High Summer,Autumn Rain,Late Autumn, and Winter, and the interannual rainfall variations for each season were analysed.Results show that for each natural season there exists tendency that in one period of several years the rainfall was above normal, while in another, below, and during the wet period not only more rainfall was recorded, but the frequency of the extremely wet year is far much higher than that of the extremely dry year, while the wet period shows just the opposite except in the winter season. Finally, based on the staistical regularity on the occurrences of wet period, dry period, and calamityprone period, a perspective is made on the rainfall tendency for the years before 2000 to provide some help to the agricultural planning, and the prevention of calamities.