There are multi-layer opening plates in the main air duct of the ship "s engine room, which seriously affects the ventilation performance of the main air duct. Based on computational fluid dynamics (CFD), the ventilation numerical simulation of the main air duct with different opening plate types was carried out, and the motion characteristics of the airflow under internal obstacles were analyzed. The results show that when the air outlet is far away from the air supply outlet and needs long-distance air supply, a diversion-type opening plate can be set to make the distal air outlet obtain greater air volume. When the wind speed of the outlet near the air supply outlet is large, the topology optimization opening plate and the original opening plate are better than the diversion opening plate. Under the same air supply condition, the performance of topology optimization type is better than that of original type in all aspects.