Abstract: The expansive deformation caused by rainfall is one of important factors for the failure of expansive soil slopes. Therefore, it is of great practical significance to analyze the progressive failure process of expansive soil slopes under rainfall. Based on the linear relationship between expansion strain and matrix suction increment, a numerical analysis method for multi-field coupling of unsaturated seepage, stress and expansion strain fields is proposed. Based on the strain-softening model, the infiltration process of an expansive soil slope induced by single rainfall and the complete process of its progressive failure are presented. The results show that the progressive failure of the unsaturated expansive soil slope occurs at the foot of the slope and extends gradually to the top. It has the characteristics of time delay, multistage and retrogression. The expansive and strength parameters of expansive soils have significant influences on the failure form of the slope. The failure of expansive soil slopes retains the commonness of the general cohesive soils and presents the particularity of dry shrinkage and wet expansion.