Abstract: Using the self-developed flume, the model tests are conducted to trigger heavy rainfall-induced failure of cohesionless soil slopes with Japan silica sand No. 6, No. 7 and No. 8 under the fixed rainfall intensity of 90 mm/h. The failure process is described and the effects of slope thickness and unloading at the leading edge, and the particle size and fine-particle content on the failure process are discussed. Moreover, the response of pore-water pressure in the failure process is also studied. The results show that: (1) Under the sustained heavy rainfall, the failure process of cohesionless soil slopes can be divided into three stages, i.e., rainfall infiltration, initial failure and major failure. (2) At the major failure stage, the tension cracks gradually appear from the toe to the middle, shoulder and top of the slope. The failure mode is controlled by the particle size of soils and fine-particle content with the mechanism of the extent of shear dilation effect. (3) The smaller the slope thickness is, the shorter the duration of failure process is, while the smaller the sliding distance and velocity are. In addition, unloading at the leading edge can accelerate the failure process of the slope, and make it have a longer sliding distance and a larger sliding rate. (4) When the deformation of the saturated slope is accelerated, the excess pore-water pressure is generated at the sliding surface, and then the sudden sliding is induced. At the same time, the pore-water pressure at the sliding surface decreases sharply due to the decrease of slope thickness and the occurrence of shear dilation effect.