Abstract: According to the symmetrical characteristics of groundwater table in horizontal drainage system,a kind of isolation body is selected to study the law of groundwater movement in the body of slope.The drainage hole is simulated as a type of conductive pipe with strong permeability, the seepage model of the isolation body is establishes. Adopting the numerical method,this paper simulates and analyzes the seepage distribution features of groundwater in the dewatering process of the horizontal drainage holes.It is shown from a practical example that the reasonable results can be obtained,the method can be used in assessment and design of horizontal drainage project.