Abstract: Investigation shows that many newly excavated expansive soil slopes considered to be stable in computational analysis become unstable and damaged.A detailed research on this problem was carried out by use of a geo-centrifuge model.Test results indicated that the dry-wet cycling was the main factor of the problem.The dry-wet cycling led to cracks in the slopes.With the increase of the times of the dry-wet cycling,the width and the depth of the crack got larger and deeper.The crack not only weakened the soil structure of the slope,but also provided passage for water penetration,which further led to soil softening and strength decrease.Each dry-wet cycling resulted in the accumulation of the downward settlement and horizontal displacement of the slopes.With the increase of times of the dry-wet cycling,the expansive soil slopes became gradually damaged no matter what soil density was.Since the triaxial tests in the lab can not simulate the formation and process of the cracking and the water penetration process in the expansive soil,it is not proper to directly use the strength and deformation data obtained from the triaxial tests for the analysis of the deformation and stability of the expansive soil slopes.The key measure to prevent the damage of the expansive soil slopes is to stop the water exchange with the outside.If water exchange could not be stopped,some drainage measures should be taken to prevent the wetting of the slopes.