Discontinuous deformation analysis （ DDA ） is used to simulate the failure process of expansive soil slopes ． According to the characteristic of shallow landslide of expansive soil slopes and the Mohr-Coulomb criterion ， three groups of potential failure planes, which cut each other and generate block system, are assumed. On the basis of experimental data, relationships between the material parameters and the water content of expansive soil are assumed ． The strain of hygroscopic expansion is treated as initial strain ． The computed result shows that shallow landslide of an expansive soil slope happens after swelling and shear strength reduction due to the moisture absorption. This result is in accordance with the failure of expansive soil slopes in practice. The calculation model established in this paper provides a sound base for further studies of stability and reinforcement measures of expansive soil slopes.