Abstract: By using the geotechnical centrifuge of Tongji University and combining with an artificial rainfall simulator which is designed to control the rainfall intensities, the centrifugal model tests are carried out to study the macro-mesoscopic formation mechanism of cohesionless soil slope failure induced by rainfall. During the test processes of slope failure, the pore pressure is measured by the high-speed dynamic data acquisition instrument and the precise pore water pressure sensor. Using the HD digital imaging equipment and the mesoscopic structure analysis software Geodip, the variation laws of soil microstructure during the formation of landslide are analyzed. The results show that the permeation and cumulation of rainwater in the slope body is regarded as the main cause of slope failure. The formation mechanism of landslide is the motion of the fine particles with migratation of pore water in the slope. The gathering of rain at the inner slope body causes the increase of pore pressure and the reduction of soil strength, and then the whole sliding occurs when the sliding force exceeds the shear strength of soil.