AbstractGroundwater lowering has brought a great impact on high speed railway. It has developed a measurable regional settlement of subgrade and also made a negative impact on piles under subgrade. In this paper, two structure types, namely P-R structure and P-N structure under subgrade have been considered at different groundwater lowering rates. Plaxis 3D is employed to assess subgrade center point's settlement, piles’ negative skin friction, increment of skin friction in piles and piles’ axial force. From the results, we can figure that groundwater lowering indeed has a negative impact on subgrade and the maximum negative skin friction of piles can increases up to 30-40 kN/m. The axial force in piles can be twice as initial conditions.