Abstract：Sandy clay and sandy loam are the two typical kinds of soils along the Qinghai-Tibet railway. Under an open system environment，the two kinds of soils are tested in repeatedly freezing and thawing circulation experiments. In these experiments，all the soil samples are tested at the different dry density，water content and temperature. The results show that the final dry density is a constant after the repeatedly freezing and thawing. The final dry density of sandy clay is 1.55 g•cm－3，while that of sandy loam 1.78 g•cm－3. It can also be concluded that the final dry density of each soil sample depends on the soil type but not the original dry density. The repeatedly freezing and thawing circulation can change water content of soil. After the circulations，the water content of soil will increase，and the water content at the top part is greater than that at the bottom part due to water migration from bottom to top.
