Abstract: Heavy rainfall can pose serious risks to the ecological system in mountain and loss areas. The intense rainfall infiltration in a short period can also cause soil and water loss on the slope surface, tensile cracks at the top of the slope, and the formation of dominant channels within the slope. Subsequently, erosion and damage of the slope can often occur after infiltration. It is very urgent to investigate the erosion mechanisms underlying loess slope failure under heavy rainfall. This study aims to dynamically monitor the variations of moisture content within the slope, the infiltration rate, the advancement of the saturation surface, and the evolutions in displacement. The study area was taken as the Yangling Loess in China. Large-scale model tests were also conducted to systematically examine the erosion process. The erosion mechanisms of loess slopes were then determined to couple the gravity and hydraulic forces. Finally, engineering recommendations were proposed to prevent slop erosion under heavy rainfall. The results indicated that: (1) A great variation was observed in the content of the moisture on the slope surface under rainfall, such as "rapid increase during rainfall - tendency towards stability - decrease after a rainfall - tendency towards stability" and "unchanged in the early stage of rainfall - rapid increase - tendency towards stability". Nevertheless, the content of moisture only increased partially within the slope. Consequently, the closer to the slope surface was, the lower the soil strength and the more vigorous the movement was. The infiltration rate (v₁) of the wetting front gradually diminished with the increase of infiltration depth. The v₁ at the slope top was approximately three times that at the slope surface. Hence, its infiltration depth was greater than that of the slope surface. The wetting front in the slope top region also presented an inverted S shape. Furthermore, the wetting front in the slope surface region was basically parallel to the slope surface. (2) The erosion of loess slopes was classified into three stages: local cracking (first at the slope top and then on the slope surface) - the development of erosion gullies and cracks at the slope top - slope surface sliding erosion and slope top collapse (first on the slope surface and then at the slope top). Among them, hydraulic erosion involved soil softening and local cracks, followed by the formation of erosion gullies and fracture development, and ultimately resulted in surface runoff erosion. Gravity erosion was characterized by the solifluction - crest crack - crack coalescence and crest collapse. Mixed erosion was advanced degradation under both hydraulic and gravity erosion, resulting in more extensive and severe damage. (3) The control measures were given for the erosion and damage on the loess slopes. The surface erosion was reduced to lower the infiltration quantity at the slope top. The slope surface was covered with ecological bags, in order to prevent erosion during ecological restoration. Some measures were also implemented at the top of the slope to minimize the infiltration of rainwater from the top. The entire surface of the slope was sprayed with cement mortar to form the protective layer on the slope and the top of the slope, thereby avoiding rainfall infiltration. This finding can offer scientific prevention and control measures for the erosion and damage of loess slopes in the northwest area under the action of rainfall.