Droughts and floods from 1961 to 2006 in summer drought seasons in Hunan Province are analyzed by using z index, and the variation characteristics of multiscale drought and flood activities are analyzed by the wavelet analysis method. The results show that there was a significant increasing trend in the flood index in the past 46 years; floods occurred more frequently from the 1990s. It is also found that there were significant periods of 22 years, 12 years, 6 to 7 years, 3 to 4 years in the flood index, and significant periods of 20 years, 10 years in the drought index. Relation analyses between 500 hPa height and z index show that there existed good correlation between z index and 500 hPa height, especially in February. In heavy flood years, 500 hPa anomalies were prominently negative in the eastern Siberian and positive in the subtropical high pressure zone; in contrast in heavy drought years, 500 hPa anomalies were obviously positive in the eastern Siberian and negative in the subtropical high pressure zone.