Abstract: The mechanical effects of root systems in vegetative bank protection can significantly enhance the shallow stability of slopes. However, research on how changes in hydraulic and mechanical effects of roots under conditions such as rainfall and water level fluctuations impact shallow slope stability is limited. This study employs numerical analysis methods to simulate the hydraulic effects of root-soil composites on slope seepage fields during transitions from unsaturated to saturated states (rainfall conditions and rising water levels) and from saturated to unsaturated states (falling water levels). Additionally, the influence of root-soil composites on shallow slope stability under different hydraulic characteristics is analyzed. The simulation results indicate that: (1) Within the three specified rainfall intensities, the preferential infiltration effect of root-soil composites is positively correlated with rainfall intensity and duration, while the drainage effect is negatively correlated with both. Under prolonged light rainfall or short-duration heavy rainfall, the negative impact of the hydraulic effects of root-soil composites predominates due to the increased depth of rainfall influence. (2) Under falling water levels, the drainage effect of root-soil composites exhibits a lag, with mechanical effects remaining dominant; under rising water levels, the infiltration effect of root-soil composites strengthens with increasing water level rise rates, gradually overshadowing the mechanical effects. These findings provide valuable insights for the application of vegetative bank protection engineering. Even when using ecological vegetative bank protection, it is essential to enhance surface and subsurface drainage measures.