Abstract: As its effective for reducing vibration and noise reduction, viscoelastic damping treatments have been widely used on ship hull.However, it is necessary to optimize size and other design parameters of damping treatments for reducing noise&vibration, which can achieve the best effects with additional weight as little as possible.Firstly, this paper introduces theoretical formula derived by complex stiffness method for free and constrained damping treatments, and structural loss factor are analyzed theoretically, then damping structure and material parameters can be identified.Extensive 1: 2.5 scale ship cabin model is tested using modal hammer measurement method, which can accurately assess the damping capacity.The test results show that:constrained damping treatments can considerably attenuate structural resonance amplitude.while 1.7 mm thick of constrained damping treatments is bonded to 2.5 mm thick cabin plate, the maximum vibration reduction is 11 d B, the maximum noise reduction can reach to 9 d B.Finally, cabin noise level have been measured for sailing ship under constrained damping treatments, and all measured noise levels can meet the IMO-468 criterion.