Abstract: The e xpanding velocity and expansion ratio of the original expansive soils are studied by means of the indoor free expansion ratio tests and linear swelling ratio tests. According to the vertical load, the expansion processes of the expansive soils in one-way immersion under different vertical load s are divided into three types, namely no load acting, small load acting and big load acting, and are separately divided into different parts. The trends of expansion ratio, dry density post expansion, void ratio post expansion, moisture content post expansion under different loads are investigated. It is shown that along with the increase of loads the expansion ratio under loads, void ratio post expansion and moisture content post expansion decrease, and the dry density post expansion increases. The ultimate vertical expansion ratio has a positive semi-logarithmic linear correlation with the water absorption rate . According to the allowable deformation of the soils of the project, the allowable expansibility is determined. Then the retaining wall is designed.