According to the extensive application of shield tunnel, large-diameter shield tunnel in particular, a simplified seismic design method is in urgent need. The equivalent static method is more suitable for the rigid underground structure, rather than flexible structure such as large-diameter shield tunnel. In this paper, shield tunnels with different diameters and thicknesses are analyzed and calculated by time-history method and free field deformation method. The calculation and analysis above help to identify the stiffness ratio to measure the relationship of structure’s stiffness and soil’s stiffness and the derivation of a revised stiffness solution based on the free field deformation method. The results indicate that this method can calculate seismic stress of shield tunnels with different diameters and thicknesses accurately.