Abstract: For the expansive soils of Nanning in Guangxi province of China different drying environments are acquired to test the shrinking characteristics and water retention by setting different temperature and humidity conditions. The unsaturated permeability curves under different drying rate are predicted. The infiltrating process of cut slope is numerically simulated. The test results show that the slow drying rate produce a large shrinking deformation. The sustainable evaporation with high humidity results in a large potential swelling deformation in shallow strata. The numerical computation indicates that an evaporation process of slow drying rate produces a large infiltration depth. It is concluded that the sustainable evaporation with high humidity induces a large infiltration depth, which is adverse to the stability of cut slope of expansive soils.