Abstract: The matrix suction in the unsaturatedsoil is closely related to its micro pore structure.In order to analyze the response laws of the pore structure and matrix suction of the slip zone soil under the actions of the wetting-drying cycles, the remolded slip soil of Huangtupo Iandslide was taken as the research case history.Further, a mercury intrusion porosimetry (MIP) tests are carried out to study the changes in pore size distribution during the wetting-drying cycles and the pore size distribution curves for different cycles have been got.On this basis, the pore of slip soil is classified into three type (large pores, medium pores, and small pores) using the fractal theory, and the soil-water characteristic curves of the slip zone soil is indirectly calculated (SWCC) using the capillary model.The research results show that under repeated wetting-drying cycles, some small pores gradually transformed into large pores, and some particle pores changed into aggregate pores.The curves had a common inflection point, and above the inflection point the matrix suction under the same water content gradually increases with the increase in cycle numbers, however, the opposite behavior was noted below the inflection point.Hence, the results obtained from this research can be helpful in comprehensively understanding the wetting-drying effects of the slip soil, which is of great significant and can be applied to research on the evolution mechanism of reservoir bank landslides.