To enhance the vibration suppression capability of bearing housings in the motor propulsion systems of underwater vehicles, a structural optimization method based on high-damping manganese-copper (Mn-Cu) alloy is proposed as an alternative to conventional titanium alloy. Periodic weight-reduction holes are introduced in the sleeve region of the bearing housing, while key installation interfaces are retained, in order to control the overall mass increase associated with the material substitution. Finite element simulations are carried out to systematically investigate the effects of hole diameter and spacing on the stiffness, strength, and thermal expansion performance of the housing. The relationship between geometric parameters and mechanical behavior is clarified, and an optimized configuration with balanced performance is identified. To further verify the effectiveness of the design, vibration transmissibility tests are conducted. The results show that the Mn-Cu alloy bearing housing exhibited significantly lower vibration transmissibility than its titanium counterpart within the frequency range of 0-500?Hz, which indicates superior low-frequency vibration attenuation performance. It is demonstrated that high-damping alloys can maintain essential mechanical properties while significantly improving vibration isolation characteristics with proper structural optimization.