Abstract: In recent years, many linear loess fill slopes have appeared with the continuous development of “Governing valleys” and “Retaining plateau” projects in the Loess Plateau. Slope instability is induced by rainfall, which is an important factor. However, there are few studies on the deformation evolution characteristics and failure modes of rainfall-induced linear loess fill slopes. In this paper, the linear loess fill slope is taken as the research object, and the indoor rainfall model test is carried out through sensor monitoring, three-dimensional laser scanning technology and artificial rainfall system. The hydrological response characteristics and failure process of slope under rainfall infiltration are recorded, and the wetting front, soil particle migration, internal deformation response, fracture evolution characteristics and failure mode are analyzed. The test results show that with the infiltration of rainfall, when the wetting front is reached, the volumetric moisture content increases and remains stable at the maximum, while the matric suction decreases and remains stable at the minimum. The gully has a greater impact on the fill slope. The development of slope changes the characteristics of the water content in the slope, and at the same time it is the boundary that controls the overall sliding of the slope. The deformation response area of the slope is mainly the front accumulation area and the back slide area of the filling slope. The cracks evolve from the leading to the trailing edge, and its development offers preferential seepage channels for the infiltration of rainwater. At the same time, the cracks also intensifies the deformation and failure of the slope. The hydrodynamic force formed by rainfall drives the loss of fine particles in the slope from the rear edge of the fill slope to the front edge, weakens the cementation among the soil particles, reduces the shear strength, and causes the slope instability and failure. Therefore, under the rainfall infiltration, the deformation and failure modes of the linear loess fill slope are: gully failure at the top of slope and toe softening →local traction collapse and overall instability → block segmentation and at last the flow slip failure. The research results can provide a theoretical reference for the engineering construction of linear loess fill slope and the prevention and control of landslide disaster.