Abstract: The cyclic swelling behavior of compacted expansive clays is discussed in this paper. It shows that the swelling shrinkage behavior of expansive clays is not completely reversible. The experimental data indicate that upon repeated wetting and drying, the swelling rate of soils becomes faster. And every cycle results in decreasing swelling ability although the total swell percent increases. Furthermore it is noted that the second and third cycles cause the major reduction in swelling potential as the number cycles increases, and the soils reach the equilibrium in which no more reduction of swelling potential is caused. Finally, the authors consider that these properties are related to the integration of clay particles and the rearrangement of microstructure.