Chaohu Lake, situated in Anhui Province, is one of the five largest fresh water lakes in the middle and lower reaches of the Changjiang River with a total area of 800 km². The Chaohu Lake basin was formed in Mcsozoic era and early Cenozoic era, then developed into an alluvial] plain in the age of Pleistocene. Under the joint influences of climate, the corresponding changes of sea level and evolution of the channel of the Changjiang River, the basin began to be filled with water and became a lake in Late Holocene. The lake was formed about 2000 years ago. So Chaohu Lake is a typical riverine one with intense water body exchange. The sediments range from 5 to 6 ф in medium size and five major sedimentary types can be found in this lake, such as like-cuspat delta, open lake deposition, etc. The sedimentation rate is different in three parts of the lake, i.e. 0.21cm/a. in the cast, 0.37 cm/a. in the west and 0.14cm/a. in the middle of the lake. Total mass accumulation of the sediments in this lake is about 0.93 million ton/a. Sediment dating shows that serious pollution began in the 1970s. Sources of phosphorus arc both from allochthonous and inner loading(sediment), with about 220.56 ton/a releasing from the sediments, which has a great influence on the eutrophication of Chaohu Lake.