Abstract: On the basis of the summer (June-August) precipitation data of China in the recent 31 Years (1951-1981), we divide into Drought-Flood years and months, and select the last four years (1978-1981) as an example.In 1978, the Southern provinces of China were in severe drought. In 1979, except for some local regionas in drought or flood, generally they were in normal year. In 1980, Southern China was wet and Northern China dry and in 1981 Western China wet and Eastern China dry. By using steamline field, potential equivalent temperature and moisture, we discuss the relationship between the interannual variation in summer monsoon and Drought-Flood. We here mainly analyse low latitude 700mb surface of the southern and northern hemisphere for 1978-1980, so as to understand some relationships between different original cnrrents of summer monsoon and Drought-Flood. The results are as foollows. 1. In the severely drought year of 1978, the position of subtropical high was by east and by north and meridional cirulation prevatiled China was under the influence of intense SE current, The cold air was so weak that drought was persistent in the southern part of China. 2. In 1980, the streamline field was apparently different from that of 1978. The situation of subtropical high was by forward west and permanent stable. Three different currents influenced China, east of 110°E It was the SW current from the ahead ridge, SW current was also present coming from the Bay of Bengeal and the crose equator current, These three systems of thermal and moist currents were convergent at the southern part of China. Simaltaneously the northern cold air moved southward continuously, so that rainfall was persistent in Jianghuai river, and thus became anomalous climate of Southern flood and Northern drought in China.3.During 1979, the subtropical high normally moved from south to north.Both thermal and moist sw current (coming form northwest Pacific Ocean and the Bay of Bengal) stretched forward to China and rainfall was nearly normal.Therefore the interannual variation of summer monsoon and the sitation and strenght of subtropical high are closely associated with the low latitude circulation of the southern and northern hemisphere.