To enhance the vibration suppression capability of bearing housings in the motor propulsion systems of the underwater vehicle, a structural optimization method based on high-damping manganese-copper (Mn-Cu) alloy was proposed as an alternative to conventional titanium alloy. To control the overall mass increase associated with the material substitution, the periodic weight-reduction holes were introduced in the sleeve region of the bearing housing, while key installation interfaces were retained. Finite element simulations were 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 was clarified, and an optimized configuration with balanced performance was identified. To further verify the effectiveness of the design, vibration transmissibility tests were conducted. The results show that the Mn-Cu alloy bearing housing exhibits significantly lower vibration transmissibility than its titanium counterpart within the frequency range of 0~500 Hz, which indicates superior low-frequency vibration attenuation performance. High-damping alloys can maintain essential mechanical properties while significantly improving vibration isolation characteristics with proper structural optimization. A feasible approach and theoretical support are provided for its application in the complex power equipment.