Based on shear beam theory, the seismic response of the slope is obtained under the condition of horizontal earthquake excitation. Because mass of soil nailing is small compared to one of soil, inertia force can be ignored. The movement of soil nailing and soil is nearly in phase and damage of soil nailing depends on the size of the deformation to withstand but not inertia force, so the soil nailing is simplified for one dimension elastic rod without mass. The seismic response of soil nailing is derived through compatibility of deformation and Hooke’s law. The method is applied to a project case to carry out seismic analysis and design. Using finite element software (ADINA) to verify the proposal method the results show that the design and the analysis are safe and credible. The calculation method provides theoretical basis for earthquake analysis and seismic design of soil nailing supporting structure.