Abstract: Shallow slope failures in residual soil slopes are common in tropical and subtropical regions. These shallow failures mainly resulted from the reduction in matric suction induced by rainfall infiltration. An analytical solution of water infiltration into an infinite slope is presented on the basis of the two-dimensional governing equation for unsaturated flows. To obtain the analytical solution, it is assumed that both the soil-water characteristic curve and the permeability function can be described by using exponential functions. The analytical results are compared with those obtained from the numerical simulation, indicating that the analytical solution is reasonable. The distribution profiles of the matric suction obtained from the analytical solution can be incorporated into the limit equilibrium method to evaluate the effect of rainfall infiltration on slope stability.