Abstract: The post-earthquake flow deformation of dilative sand is associated with the compulsory water absorption due to seepage water inflow in boundary value problems. A simplified procedure, which can both reproduce the diffusion and migration of excess pore water pressure and describe the behavior of sand under water absorption conditions, is employed to study the effect of different soil profiles and soil permeability on the post-earthquake flow deformation of sand slopes. It is found that the flow deformation always concentrates on the interface where the flow of the seepage water is blocked. The thicker the liquefied layer beneath the interface is, the larger the water absorption amount of the sand on the interface is, and hence the flow deformation is larger. The amount of flow deformation can be reduced greatly by setting drainage columns to mitigate the accumulation of the excess pore water pressure beneath the blocking interface. More importantly, it is suggested that the rate of flow deformation should be controlled by the permeability of soil, and the viscosity of the materials can be ignored practically.