Aquaculture vessels are one of the new ways to expand the space for offshore farming, and if particles such as undigested feed residues and excreta cannot be discharged in a timely manner during the shipboard tank farming process, it will have a serious negative impact on the health of fish and their growing environment. The article uses FLOW-3D software to carry out numerical simulation calculations to study the effect of the number of outlets in the aquaculture tank of the 300 000 t-class aquaculture vessel on the flow field characteristics under the stationary condition, and on this basis to explore the removal effect of particles with different particle sizes and densities in the tanks. The results showed that： when the total inlet and outlet flow rate and the total area of the outlet are constant, as the number of outlets increased from 1 to 4, V_99% decreased from 0.244 m/s to 0.232 m/s and V_95% decreased from 0.215 m/s to 0.203 m/s. As the number of outlets increases, the flow velocity in the aquaculture tank decreases. Measured by the time it takes for 95% of the total amount of particles to be discharged from the aquaculture tank, when the particle density was 1 050 kg/m³, discharge of particles with a particle size of 1 mm took about 24 minutes, discharge of particles with a particle size of 0.5 mm took about 45 minutes, and discharge of particles with a particle size of 0.1 mm took about 78 minutes. So at the same density of particles, as the particle size of particles increases, their retention time in the aquaculture tanks decreased and their removal efficiency increased significantly. When the particle size was 1 mm, discharge of particles with a density of 1 100 kg/m³ took about 15 minutes, and discharge of particles with a density of 1 150 kg/m³ took about 11.6 minutes. When the particle size of the particles was the same, the higher the density of the particles, the shorter their retention time in the flow field of the aquaculture tank, and the greater their removal efficiency. In this study, an integral analysis method combining CFD numerical simulation and mathematical statistics was formed to provide research means and theoretical basis for the complex working conditions with different transverse rolling periods and larger transverse rolling amplitudes.