Abstract: Mercury poUudon has been generally recognized as a global environmental problem. It is particularly the case with mercury pollution of soils because it is well concealed, irreversible and long-continued, being a great potential threat to the terrestrial ecosys- tem. Therefore it is very important to make clear the source of Hg in soils. Based on an analysis of vertical soil profiles and soil-form- ing processes in the Dongting Lake area, Hunan, the authors find that there is a good correspondence between the Hg content in topsoils and that in soil-forming parent materials. The soil-forming processes also have significant influence on the Hg content in soils.