<p>Earthquakes and rainfall are two primary triggers of landslides, and their continuous actions significantly amplify the risk of instability for sandy slopes. To investigate the nonlinear dynamic response and failure evolution mechanism of sandy slopes subject to ground motion before and after rainfall, a series of shaking table tests were conducted. Quantitative analyses were performed to study the dynamic properties, acceleration response, and instability evolution of slope soils considering ground motion with different intensities. The results indicate that the slope nonlinear behavior is influenced by ground motion intensity and sustained rainfall. Sustained rainfall induces significant changes in soil structure, leading to a reduction in natural frequency and an increase in the damping ratio of the sandy slope. Subsequent seismic excitation further accelerates crack propagation within the slope. As ground motion intensity increases, the tensile cracks on the slope surface connect with internal shear cracks, resulting in slope instability and failure. The failure process can be divided into four stages according to the macroscopic deformation of slope models and the variation characteristics of the relevant physical quantities: early deformation, crack initiation, accelerated degradation, and overall sliding. The shaking table tests effectively reveal the dynamic response and failure evolution mechanisms of sandy slopes subjected to sequential ground motions before and after rainfall, offering valuable insights for seismic slope design and disaster mitigation in rainfall-prone regions.</p>