Abstract: To effectively suppress the vibration of cylindrical shell structures, a constrained damping structure with adjustable pre-tension force is designed in this paper. First, static and modal analyses of the cylindrical shell are performed using the finite element method to obtain its inherent vibration characteristics. Subsequently, a modal testing system is established, and frequency response functions and modal damping ratios of both the bare cylindrical shell and the constrained damping composite structure under different pre-tension forces are obtained through sine sweep tests. The experimental results indicate that the proposed constrained damping structure can effectively reduce the acceleration response amplitude of the cylindrical shell and significantly increase its modal damping ratio. Increasing the pre-tension force on the constraining layer further enhances the vibration suppression effect in the mid-to-high frequency range; however, this effect is mode-dependent, showing varying optimization outcomes for different vibration modes. This study validates the tuning effect of pre-tension force on the performance of constrained damping and provides an experimental basis for the vibration reduction design and optimization of such structures.