The accumulated plastic strain and the pore water pressure of the soft clay under traffic loading condition were given by empirical models. Based on the layer wise summation method, a pseudo-static method is proposed to calculate the long-term settlement of the soft subgrade. The settlement is obtained by the superposition of two deformations, the one is the deformation caused by the accumulative plastic strain of the soft soil induced by undrained cyclic loading; the other one is the deformation caused by the dissipation of the accumulative pore water pressure. According to the experimental data of the dynamic hollow cylinder tests, the parameters for the empirical model of the accumulative plastic strain and pore pressure are established. The stress distribution induced by the traffic loading in soft subgrade is obtained by the integration of the elastic analytical solution; and the calculation method of the total deformation is proposed by the layer-wise summation method. The proposed method has been used in real engineering projects; its rationality is verified by comparing the calculated settlement with the field measured result and the existing solution.