Abstract: The statistical relation between the hard rain area and the low lev e jet over South China during the earlier rainy season,as well as the basic features of vorticity,divergence and vertical circulation about the jet and related synoptic situation are analysed in this paper.It is pointed out that though the medium or meso scale systems which are responsible to hard rain and the jet stream are interrelated, they differ from each other.The divergence and vertical circulation about the jet axis depend on the activity of the medium or meso scale systems.The hard rain area depend to a large extent on the behavior of these systems under various synoptic patterns.