Abstract: "Southern Jiangsu" covers the part of Jiangsu Province South of the Yangtze R. roughly by Maoshan divided Mountains, It is into two parts, the western hilly country and the eastern Taihu plain.In the late Pleistocene, when the sea level was lower, the coastline nearly coincided with present isobath of 115m in East China Sea, The land at that time tended to slope gently from SSW to NNE,In the early and middle Holocene, when the climate of the whole world became warmer, the sea level rose rapidly, and the sea water flowed into the depression of the Taihu through the Wusong R., a branch of the Yangtze, and further into the depression of the Zhaohu and the Gehu through the lod Longxe R., Two bays were formed, which later changed into two lagoons. This process is proved in this article by the petrologic character and fossils of the sedimentary rocks in to profile shown by a number of holes drilled around the Taihu and Zhaoge lakes.According to historical records, in the late Holocene, the Taihu and Zhaoge lake areas were freshened through the stages of lagoon and transformed into networks of waterway. And finally they have the present landforms.