Abstract: In this paper,the discharge of Yangtze River at Hankou is used as an index to denote drought and flood years in the region of the upper and middle reaches.All mean discharge data during June-Sept.from 1865-1981 may be divided into three different groups by two indicatrixes.Statistical test shows that this classification was reasonable and applicable for hydrological analysis.Based upon what diseribed,these two series group can be classified as 5 types by mean cluster analysis,i.e.summer drought,summer and autumn drought,summer flood, late summer flood,and summer and autumn flood.In addition,the characteristics of hydrology and circulation for each type have been discussed in detail here. According to 18 primary factors,which the correlation coefficient in reference to Hankou’s discharge is≥0.5,the discharge forecast at Hankou from June to Sept of 1982 has been made.The values forecasted are as same as those observed.