Abstract: More than ten neolithic cultural sites have been discovered in the eastern part of Jiang-Huai area, showing a cultural sequence consisting of the Longqiuzhuan culture(7 000?6 300~5 500 aBP),Dawenkou culture (5 500~4 600 aBP)and Longshan (YueShi)culture (4 300~3 450 aBP). During the period of Holocene optimum,due to the joint action of favorable climate, rapid development of the Yangtze and Huai river delta and sea level changes, land was expanded eastward about 7 000 aBP. Multi-channel sand bars and lagoons were developed. As the result, the lowland of LiXiaHe area was formed. The environment provided favorable conditions for the survival of aquatic animals, large mammals and plants and the settlement of human being. During the YueShi cultural stage (3 450 aBP years later), however, the climate became mild and slightly dry, and the Jianghuai area was dominated by salt marshes under frequent tidal flooding, that forced the ancient residents to move away and caused the break of cultural records. It suggests that palaeoenvironmental changes is the main factor to the rise and decline of prehistoric cultures.