As a key component of power system protection devices, the high-speed earthing switch (HSES) plays a vital role in rapidly grounding faulted sections during grounding faults, thereby enhancing the safety and operational stability of the power grid. The contact system, serving as the core conductive and force-bearing part of the HSES, is directly affected by the electrodynamic forces induced by short-circuit currents, which significantly influence the switching performance and electrodynamic stability. This paper investigates the electrodynamic behavior of the contact system in a 252 kV environmentally friendly gas-insulated switchgear (GIS)-based HSES. A combined approach of theoretical analysis and finite element simulation is employed to evaluate the mechanical response of the contact structure under short-duration, high-magnitude fault currents. The results demonstrate that the contact system exhibits robust electrodynamic stability under extreme current conditions, meeting engineering application requirements. The theoretically calculated Holm force is 10.383 N, while the simulated value is 10.657 N, with a relative error of 2.64%, verifying the accuracy and reliability of the modeling methodology. Furthermore, the influence of short-circuit current amplitude and the number of contact fingers on the Holm force is analyzed, providing a theoretical foundation for the optimization and design of HSES contact systems.