Abstract: In order to study the law of water flow migration in multi-layer soil slope， the homogeneous soil slope model and the multi-layer soil slope model were established. The temporal and spatial characteristics and influencing factors of water flow migration were explored， with the development of saturated-zone taken into account， based on the governing equation of moisture content and matrix suction in multi-layer soil slope derived from the VG model. The relationship between water flow migration and effective stress was also studied. It is found that the difference in the matrix suction in the horizontal direction decides the change of water flow migration mode and the rate of change of matrix suction along the horizontal direction determines the rate increment of water flow horizontal direction. The formation of the saturated-zone is a necessary condition for forming the vertical water flow. After the rainfall stops， the down-slope water flow is rapidly generated only in the shallow layer of 0~1.3m， with the forming of down-slope water flow in deep area lagging behind. The horizontal water flow at the interface of two layers of soil with large differences in permeability changes sharply， and the forming of up-slope water flow is always accompanied with the decrease of effective stress.

Key words: rainfall infiltration, unsaturated soil, water migration, matrix suction, multi-layer soil slope