We used the data of temperature and salinity of the coastal marine stations to analyse the characteristics and obtained some evidence: the change of salinity near the Weizhou island in Summer coincided with the east and center parts of the Qiongzhou Strait,which implied that the water of the South China Sea in Summer enters into Beibu Bay via the Qion.

In this paper why we should study the South China Sea warm water is explained and today s research results are described and some questions which should be studied about seasonal and interannual variability of the South China Sea warm water are proposed.