Abstract: On the basis of the structural dynamic optimization design theory，this paper investigates the structure of the composite pedestal of a typical submarine double cylinder shell with high transmission loss. To achieve the optimum vibration reduction，the exact sectional dimensions and positions of the rigid vibration isolation mass is first determined through preliminary optimization. Next，the rigid vibration isolation mass is equated with a bulb flat with the same section moment of inertia. By considering the restriction of the gross weight and the structural strength of dangerous sections，the structural dynamic optimization formula is established. Basically，the objective function minimizes the average vibration acceleration of the non-pressure hull for all frequencies，and the design variables such as the hole radius and the pedestal degree are carefully chosen. Results show that the composite pedestal with high transmission loss considerably reduces the vibration noise in the medium-high frequency range，where the average vibration acceleration of the non-pressure hull is decreased by 1.66 dB.