Abstract: Typical marine ships contain large amount of piping systems, and the relevant sea opening structures directly influence the acoustic characteristics of the hull.In this paper, the sea opening of typical piping systems is taken as the research subject, and an analyzing model is established in Fluent, which includes pump, piping system, hull and sea opening.Meanwhile, the sound pressure of the flow field and external field is analyzed.By comparing the optimized models for different fluent areas of the sea opening, a low noise structure is confirmed that is capable of improving the structure's acoustic characteristic significantly.Besides, the variation of the hydrodynamic noise of the whole piping system unit that uses low noise sea opening and the original structure is studied.The results indicate that the low noise sea opening of structure optimization plays a key role in noise reduction, which improves the stability of the whole fluent area and reduces the fluid pressure in the far-field.