Abstract: How to better simulate the hysteretic performance of separated shock absorber under earthquake is an important part of the seismic design of separated shock absorber. Because theoretical research on describing the mechanical properties of separated shock absorber from material level is relatively insufficient, a calculation method based on the Ramberg-Osgood model to derive the skeleton curve of separated shock absorber is proposed. Based on this method, a simplified algorithm for deriving bilinear model is also proposed. The difference in skeleton curve of separated shock absorber under the bilinear model, Chaboche model and ideal elastoplastic constitutive model is compared using ABAQUS. The applicability of the simplified algorithm in seismic design of bridge engineering is analyzed using an example of a 32 m railway simply-supported beam bridge. The results show that the skeleton curve of separated shock absorber derived based on the Ramberg-Osgood model can better fit that of the Chaboche model. Under near-fault earthquake with velocity-impulse effect, the average errors of bearing displacement and pier bottom bending moment calculated with the bilinear model and Chaboche model are −3.6% and 6.5%, respectively. The proposed simplified algorithm of bilinear model is safe and reasonable for the seismic design in bridge engineering.