<p>Low-frequency excitation is often challenging to fully absorb through internal energy dissipation systems, while grounding damping can effectively leverage the stability of the ground to absorb low-frequency energy, thereby mitigating the effects of low-frequency excitation on the primary structure. In this paper, the response mechanism of a grounded damping nonlinear energy sink (GNES) is investigated based on the complexification-averaging and multi-scale method. Furthermore, the impact of external excitation amplitude on the amplitude frequency curves is analyzed under two different primary system damping ratios, and the frequency threshold at which the GNES exhibits damping effect is identified. Besides, the vibration suppression region within the two-dimensional parameter space is partitioned into four distinct zones: the invalid region, saddle-node bifurcation region, effective damping region, and deterioration region. An in-depth analysis is conducted on the effects of varying system parameters on the damping region. Compared to the classical NES model, the numerical simulation results indicate that GNES achieves superior vibration reduction over a broader range of excitation frequencies. This finding holds substantial significance in enhancing the applicability of NES in broadband excitation environments.</p>