Abstract:Based on the daily precipitation data of flood season (from April to September) in 1960-2004 from 78 stations over the Mid Lower Reaches of Yangtze River, the extreme heavy precipitation threshold values for every station was firstly deter mined, then the extreme heavy precipitation event frequency in flood season was counted and their temporal and spatial characteristics are analyzed. The results show that the extreme heavy precipitation event f requency greatly affects the amount of total precipitation in flood season. The consistent anomaly distribution is the main spatial model of extreme heavy preci pitation event frequency over the Mid Lower Reaches of Yangtze River. The spati al distribution of extreme heavy precipitation event frequency can be divided in to five main regions. The maximum entropy spectral estimation analysis shows tha t 2-4 years period is significant in region I; the major notable cycle is basica lly the same in regions II and IV, including significant periods of 2-3 years an d 6.3 years; 14.7 years period of inter decadal variation is notable in region Ⅲ; 22 years period of inter decadal variation and 4-5 years period of inter annual variation are significant in region V. In all of the representative stat ions, Yueyang (region I) reveals a very significant growth trend, i.e. once per 10a; Nanyue (region II) and Nanjing (region IV) have a rather weak growth trend; the growth trend of Quzhou (region V) is weakest; and Hongjia (region III) show s a weak decline trend in the last 45 years.