Abstract: To analyze the dynamic impedance characteristics and evolution mechanisms of the metallic damping clamp with metal rubbers used in nuclear piping systems under high-temperature environments, the experimental tests for the dynamic characteristic of the damping clamp are conducted. A dedicated high-temperature dynamic test platform is established to evaluate the damping clamp under various preload levels at both ambient temperature (25 °C) and elevated temperature (300 °C). Key dynamic parameters, including dynamic stiffness, natural frequency, damping ratio, dynamic-to-static stiffness ratio, mechanical impedance, and energy dissipation, are measured and analyzed. The results are as follows. First, the dynamic stiffness of the damping clamp increases with increasing preload. However, under high-temperature conditions, the dynamic stiffness decreases compared to that at ambient temperature. Notably, the ratio of dynamic to static stiffness remains greater than unity under all tested conditions, indicating that the damping clamp can provide flexible static support and rigid dynamic damping. Second, regarding impedance response characteristics, as the excitation frequency increases, the impedance curve exhibits a distinct evolution pattern of fluctuation, stabilization, and re-fluctuation. When the excitation frequency grows up to close to 100 Hz, a significant trough appears in the input impedance curve, corresponding to the anti-resonance point where vibration response reaches its maximum. Under high-temperature and high-preload conditions, the frequency associated with this trough shifts toward higher frequencies, reflecting an increase in the equivalent dynamic stiffness of the system. Finally, during static compression, the damping energy dissipation under high-temperature conditions is lower than that at ambient temperature. In contrast, during dynamic loading-unloading processes, the variation in damping dissipation under high-temperature conditions is not significant; however, it increases markedly with increasing preload. These findings reveal the evolution laws of dynamic impedance and the energy dissipation mechanisms of metal-rubber damping clamps under the coupled effects of elevated temperature and preload, thereby providing important experimental basis and theoretical support for the structural design and engineering application of such clamps in nuclear piping systems under complex high-temperature operating conditions.