Abstract: To reveal the evolution law of vibration states of tandem twin-cylinder structures with wind speed under wake coupling effects, this study constructs a two-degree-of-freedom (2-DOF) tandem cylindrical system and systematically investigates its vibration response characteristics. A combined approach of two-way fluid–structure interaction numerical simulation and wind tunnel experiment is adopted to comprehensively examine the vibration response behaviors and wake evolution patterns of the 2-DOF tandem bluff bodies under varying incoming wind speeds and cylinder spacing ratios. The results indicate that, with increasing wind speed, the system vibration undergoes a distinct three-stage evolutionary process, successively characterized by a cooperative vibration stage of both bluff bodies, an upstream-bluff-body-dominated vibration stage, and a downstream-bluff-body-dominated vibration stage. This sequence reveals a progressive shift of the dominant vibrating object in response to wind speed variation. Furthermore, as the spacing between the two bluff bodies decreases, the aerodynamic excitation imposed by the wake of the upstream bluff body on the downstream one is significantly intensified, which in turn enhances the wake coupling effect between the two bodies and consequently improves the overall vibration response of the system. This study provides theoretical basis and design references for the optimization of tandem bluff-body structures, and also offers a new technical pathway for the development of flow-induced vibration energy harvesting devices under low-wind-speed conditions.