Performance degradation trend analysis of electric multiple units (EMU) bogie shock absorbers is important for scheduling maintenance plan and avoiding accidents. However, their degradation mechanism is still far from clear. The existing research does not take into account how to simulate shock absoeber in the simulation model of degradation process. Aiming at this problem, this paper analyzes the working principle of double-cycle shock absorbers of EMU, and establishes a simulation model. To be specific, AMESim is used to build the simulation model, and the accuracy of the model is evaluated according to the real measured data. By modifying the model’s parameters, the degradation process of the shock absorber is simulated, and the external leakage of the shock absorber is analyzed. Moreover, the indicator diagrams under different degradation degrees and different external leakage degrees are simulated. Finally, this model is beneficial for revealing the degradation mechanism of EMU bogie shock absorbers.