As the key equipment of the hopper system，the loading box directly participates in the loading process，and its discharge characteristics have an important impact on the effect of loading and production efficiency of the ship.Taking the loading box of a 15，000 m3?trailing suction hopper dredger as the research object，the flow field numerical simulation method is used to calculate and analyze the key parameters such as the main body size and structural form of the loading box，which affect the flow characteristics.The results show that within a certain range，the energy dissipation effect is improved as the diameter of the loading box increases，and the discharge uniformity is improved to a certain extent.Under the condition of equal cross-sectional area，the effect of loading with a circular-section loading box is significantly better than that with a square-section one.The downward velocity component at the middle openings of the loading box is much larger，which can be locally optimized by arranging two horizontal baffles.The loading box design proposed in this study can help to improve the deposition effect in the process of dredging and loading fine silt，save loading time and reduce overflow losses.