Abstract: Based on the analysis model of pseudo-static stability, a permanent displacement calculation model of slope protected by soil nailing under earthquake is established. The total permanent displacement consisted of two parts of the earthquake displacement and the post-earthquake displacement is proposed. The solution of average acceleration adopts the elastic dynamic calculating model to improve the rigidity assumptions of the Newmark method. Using genetic algorithms to search yield acceleration can achieve the permanent displacement of slope under earthquake. Employing the principle of work and energy, the calculating model of a post-earthquake permanent displacement is established and solved. According to flexible soil nailing characteristic, the “folding steps” slip deformation mechanism is proposed to calculate the sliding friction works of soil nailing after the earthquake. The dynamic design philosophy and flow chart of the soil nailing structure are given based on the control of the permanent displacement of the slope. The analytical results show that the ratio of a post-earthquake displacement to a seismic displacement is great, and the post-earthquake displacement can not be ignored.