Abstract: In order to improve submarine's hiding capacity, acoustic decoupling tile is usually covered on the surface of the hull structure. The influences of decoupling tile on underwater vibration of a complex cylindrical & cone structure (CCCS) are investigated by using statistical energy analysis (SEA) method. Mainly, the influence of decoupling tile arrangement on vibration of CCCS and the influence of damping loss coefficient on vibration reduction capacity of decoupling tile are analyzed. Study indicates that decoupling tile can reduce vibration of CCCS, and the effect of reduction varies with the arrangement of decoupling tiles and the damping loss coefficient. Vibration reduction effect of the decoupling tile is remarkable to downstream structure of CCCS, while negelectable to the upstream structure if decoupling tiles are arranged on the main stream of vibration transfer, and the vibration reduction capacity of decoupling tile is proportion to the coverage density. Research also indicates that damping loss coefficient has effect on noise reduction capacity. With the increase of the damping loss coefficient, the vibration reduction capacity of decoupling tile decreases.