Abstract: Taihu Lake is situated in the Taihu Plain, south of the Changjiang River. It covers an area of 2338.1 square kilometres,and is one of the five large freshwater lakes in China. It is proved that the Taihu Plain was not transgressed extensively when there appeared a high sea level in the Middle Holocenc by the continental deposit on the Taihu Plain, many remains of ancient culture of the early and middle Neolithic period and the peat-buried sites 5000-6500 years ago. Taihu Lake was formed by river silting up and water confluence. Taihu Lake has a large area and shallow water. Disturbed by storm, the deposit at the bottom of the lake was very thin. Wave and lake current made the west and south banks on the lake in the shape of are. The area of the lake has been expanding since its formation. The peak period of expansion appeared in the warm time of the Sui and Tang dynasties.