This study explores the seismic response differences between cut slopes and embankment slopes, with a particular focus on the impact of initial water content on the seismic performance of unsaturated slopes. To achieve this, a soil-water-air three-phase coupled numerical analysis method was developed within the framework of unsaturated soil mechanics. This numerical approach was employed to simulate the deformation patterns and acceleration responses of both slope types during an earthquake. Additionally, the influence of initial water content on the dynamic behavior of the slopes was examined. The results indicate that high initial water content reduces the risk of sliding failure in cut slopes due to the stabilizing effect of the adjacent undisturbed ground. Embankment slopes exhibit a more pronounced sliding tendency, with greater displacement observed at the slope toe.