Abstract: A series of large-scale static model tests on a compacted expansive soil slope under artificial rainfall are conducted for real-time monitoring of water content and swelling deformation. The monitoring results show that the distribution of water content in the slope is nonuniform in space and time, which results in the nonuniform distribution of swelling deformation at the drying-wetting interface. According to the survey of failure surface by excavation after landslide, it is observed that local shear ruptures firstly take place at the drying-wetting interface within the shallow layer of slope, and then extend downwards gradually with water infiltration, and multiple shear sliding surfaces are produced at different depths and areas, which connect further with each other and finally lead to an overall landslide. The traditional limit equilibrium method can not correctly simulate the progressive landslide of expansive soil slopes. The finite element method with expansive model is adopted, and the safety factor of the model test slope is calculated to be 0.92 using the strength reduction technique. Both the physical model tests and the finite element analysis prove that the essential influence factor of expansive soil slope stability is the swelling deformation instead of the over-consolidation effect and fissure presence.