Background: In the Loess Plateau region, significant engineering activities have led to many exposed loess slopes. These slopes have undergone a series of shallow failures under rainfall, significantly affecting their stability. Vegetation can somewhat restore the ecological damage to the slope surfaces and enhance their stability. Thus, studying the spatiotemporal evolution of soil moisture migration under vegetation protection on loess slopes is crucial. Methods: Employing experimental designs with slope gradients of 45° and 60°, this investigation is structured around a trio of core objectives: to delineate the processes of rainfall infiltration and its redistribution within the slope, to chart the evolution of soil water within the loess soil matrix, and to discern the impacts of slope inclination on soil water dynamics. Critical to this study are the monitoring of volumetric moisture content, matric suction, and the external variables of rainfall and temperature, alongside an analysis of soil water potential and moisture movement as observed in laboratory setups and simulated through Hydrus-2D. Results: The study revealed that slope angle significantly affects soil moisture infiltration and redistribution. The steeper slope (60°) exhibited more pronounced fluctuations in soil water potential, particularly during the rainy season, reflecting the dynamic nature of water movement. This slope also demonstrated sharper transitions in soil moisture during drying periods, indicating a greater sensitivity to weather changes. Water movement parallel to the slope surface was faster on steeper slopes, especially under drying conditions, with more pronounced lateral downslope flow at the surface layer. In contrast, the gentler slope (45°) showed more consistent moisture retention during wet periods, with slower and more uniform soil moisture movement, leading to a steadier moisture gradient and prolonged upslope movement. Vegetation plays a crucial role in modulating soil moisture dynamics, with grass growth being more effective on the steeper 60° slope. The extensive root network on this slope enhanced water retention, increased soil permeability, and reduced erosion. During the drying phase, deeper root systems significantly reduced volumetric water content at shallower depths, promoting higher moisture content in the middle sections of the slope.