Abstract: Based on the soil-water characteristic curve of unsaturated soils, a new formula for strength of unsaturated soils taking into account the influence of matric suction and volumetric water content simultaneously is established. The strength reduction FEM is introduced into the stability analysis of unsaturated soil slopes in which the generalized cohesion of unsaturated soils and internal friction angle of saturated soils are adopted as strength parameters. Without considering the change of water content (or saturation) and matric suction under short-term seismic loading, a static and dynamic finite element method for analyzing the seismic stability of unsaturated soil slopes is established. The effect of foundation radiation damping on seismic response is simulated by combing viscoelastic artificial boundary. The seismic stability analysis is validated through numerical simulations in which the finite element calculation, convergence of time-history of relative displacement on key points and plastic zone distribution are used to judge the dynamic stability of the slopes. The analyses show that although the matric suction has significant effect on the static stability of unsaturated soil slopes, the earthquake force still plays a leading role in the seismic stability analysis of the slopes.