The seismic pushover analysis method of underground structures is improved by applying the local deformation peak of the free field is used as the target displacement and the corresponding horizontal acceleration of the soil layer is used as the equivalent inertial acceleration input. The local peak deformation and method of determining the equivalent inertial acceleration are given, and the implementation steps, application, and functional characteristics of the seismic pushover analysis method for underground structures based on local deformation of the free field are introduced in detail. Compared with the pushover method, the proposed method considers the nonlinear characteristics of different buried underground structures and interactions between the soil and the structure. A complete ability curve can be obtained by analyzing the deformation and stress conditions to better evaluate the seismic performance of the underground structure. For validation, the proposed method and finite element dynamic analysis are performed to analyze three practical subway station structures. Results show that the proposed method is superior to the pushover method based on integral deformation of the free field in terms of stability and simulation accuracy and more consistent with the different input seismic waves. In the case of strong earthquakes, the calculation results are slightly larger than the dynamic nonlinear analysis results for deep buried underground structures.