Freezing tests are conducted on saturated silty soil samples with different boundary temperatures and heights to study water migration, water redistribution, frost heave and ice lens. The experimental results shows that, when temperature becomes steady, water keeps on migrating to freezing front and water content increases sharply near the freezing front and ice lens forms. The geometry of ice lenses in saturated freezing silty soil is regular without dendritic structure and frozen soil has massive structure without network of cracks. There is a starting time for frost heave, before which the water in soil is drained by the sudden freezing of the supper-cooled soil water. When the frost heave occurs water from outside supplies to the soil sample and the frost heave amount due to water inlet approximates to the total frost heave. The height of soil sample influences water migration and frost heaving amount. A higher soil sample has smaller frost heaving amount and less water content while water increment distributes more diffuse and the starting time for frost heave is longer.