Abstract: The issue of constructing buildings in swelling soil area is always a hot topic in geotechnical engineering circle, and is a hard subject in water conservancy projects. For this reason, systematic test and study of the properties of swelling soil is conducted in this paper in combination with the practical engineering work of Shuicheng Reservoir. The Shuicheng Reservoir is located in a swelling soil area, its dam is a stone-filling dam with a core wall, 59.2m height in maximum. Systematic physio-mechanical properties test and analysis, especially analysis of relationship between expansion rate, dry density, water content, and overlying pressure, are carried out. It is concluded that the expansion rate of swelling soil in this area is relatedd not only with mineral components in itself, but also dominated by natural dry density, water content, and the overlying pressure. The regularities of their relations are also got.