In 1996 the period of the Jianghuai meiyu was longer, its precipitation was more and the heavy rain during the meiyu period also happened frequently. The situation is a flooding year in the middle and lower reaches of the Yangtze River. The West Pacific subtropical high, westerly jet,the blocking patterns of high and middle latitude,and the evolution of superlong wave and long wave were analysed. The subdivision of the meiyu period in 1996 was given. The non-integer power spectrum of the total meiyu rainfall M in the middle and lower reaches of the Yangtze River in 40 years was studied, where M is the flood and drought index. It is indicated that the regional heavy flood year in 1996 is coincident with the evolution of the drought/flood periods.