<p>We have designed a nonlinear energy sink employing segmented cubic stiffness under forced excitation, outperforming conventional nonlinear energy sinks regarding vibration reduction effect. We derive motion equations and employ the method of complexification-averaging to develop an analytical framework for the system’s slow dynamics. Utilizing the multi-scale method to separate fast and slow variables, we utilize slow invariant manifold theory to reveal the system’s intricate dynamic responses. Comparative analysis demonstrates that, under identical parameters, the segmented stiffness system can induce strongly modulated responses, a phenomenon that is not observed in the traditional non-segmented stiffness system. Furthermore, energy dissipation analysis reveals the segmented stiffness system’s enhancement in both the dissipation rate and the effective frequency bandwidth for vibration reduction. Then we carried out parameter optimization. Global bifurcation analysis indicates that once the external forcing amplitude surpasses a critical threshold, the system undergoes a transition to chaotic responses, necessitating careful parameter tuning. The proposed analytical methodology offers a powerful tool for investigating segmented nonlinear systems, and the results provide a theoretical foundation for designing high-performance segmented vibration reduction devices.</p>