Abstract: Two centrifuge models were carried out in which effects of short-term and long-term infiltration of rain water were simulated by infilling water to soak the toe of expansive soil slopes with different slope inclinations.The model slopes were then brought to failure so that the process of sliding was observed and the features of failure were intensively characterized.It was shown that the domain of sliding was closely related to the increase in water content within that area caused by infiltration.In this way,it was very important to take measure to prevent increase of water content in that area near the slope toe of to soften expansive soil due to infiltration of rain water.