Abstract: By using the daily precipitation data of 81 stations in six provinces and one city in the middle and lower reaches of Yangtze River during the 1960~2003 flood season (from May to September), the annual torrential rain event genesis frequency in different stations were obtained by statistical method, and its spatial and temporal distribution in last 44 years were studied. Southern Anhui Province and Northern Jiangxi Province are the areas where the genesis frequency is the highest, while Northern Hubei and Northern Anhui the lowest. Over the middle and lower reaches of Yangtze River, the consistent abnormal characteristics is the main spatial distribution pattern. There are five main spatial distribution types: two lakes and plain type (Ⅰ), northern type (Ⅱ), Yangtze River type (Ⅲ), southern type (Ⅳ) and coastland type (Ⅴ). From the longterm change, types Ⅰ, Ⅲ and Ⅴ showed obvious increasing trend. Although the observation was not in a long-term, type IV showed decreasing trend first and then increasing trend. Type II had a slight decreasing trend. The oscillation period of these distributions are unconsistent over the last 44 years.

Key words: midlower reaches of Yangtze River, torrential rain, flood season, spatialtemporal distribution