China Academy of Space Technology has developed Meteoroid & Orbital Debris Assessment and Optimization System Tools (MODAOST) for implementing M/OD impact risk assessment and shield design optimization. Now the M/OD shield design optimization software in MODAOST has been validated by two test cases of cube and cylinder models, exhibiting its effectiveness, efficiency and stability, and it would be applied in the protection design of China's future manned spacecrafts. For further verifying the engineering practicability and effectiveness, and forming the shield optimization procedure, Japan's Pressurized Module (PM) in International Space Station is selected to implement M/OD shield optimization. According to the requirements and constrained conditions from the thickness variability of rear wall and bumper, three optimization strategies are established. Optimization results show that each optimization strategy could gain the mass saving of more than 200 kg compared with actual PM shields, which shows the effectiveness of the MODAOST's optimization function and the necessity of shield optimization.