Abstract: This paper discusses the formation,distribution and characteristics of buried peat as well as its function of purifying water in the Jianhu Plain, Shaoxing,Zhejiang Province.It is pointed out that this kind of peat was the product of the effect of lakes and swamps after regression in the middle stage of the Holocene.The peat contains more than 40% of ash and 15— 40% of humic acid,and is classified as Carex-Phragmites communis peat of low-moor type.The peat layer covers an area of 95.6km²,making up 64.2% of the whole plain.The peat layer has been dissected by a network of rivers and contacted widely with water of the lake everywhere.The peat layer along the lake has accumulated a lot of pollutants.The laboratory tests con-firm that the peat has the significant function of purifying water of Jianhu Lake. It is considered that the shallow buried peat layer distributed in other areas of the South banks of the Qiantang River and the Hangzhou Bay ought to have the similar purifying function to the neighbouring water.Therefore, the measures should be taken urgently to prevent peats of the Jianhu Plain or other areas of the south banks of the Qiantang River and the Hangzbou Bay from being excavation and destruction arbitrarily.