A numerical ocean model, ECOMsi (Estuarine Coastal Ocean Modelsemiimplicit) was applied to evaluate hydrodynamic conditions of the marine ranching planning zone (northwestern side of Baishi Mountain, Central Mountain and Tong Mountain) in Xiangshan Bay, Ningbo, coupled with a 3D Lagrangian particle tracking module to study the residence time of water and particles in this planning zone. Result shows that the bottom current velocity in the marine ranching planning zone generally complies with a restriction of the highest velocity of 0.8 m/s. We take the depth around the planning zone into account synthetically, and suggest that the artificial reefs should be located at the northwestern side of the planning zone within a range of depth from 6 to 10 meters, since in this region surface and bottom current velocities could be limited under 1.2 m/s and 0.6 m/s respectively. The tracking result of particles released within the marine ranching planning zone indicates that about 90% of particles remained west to the fjord of Xiangshan Bay for more than two months. In earlier 30 days after particles were released, the proportion of particles leaving marine ranching core zone increased rapidly, and it became steady after the 30 days. During the periods of first and second months after particles released, particles that remained within a scope of 5 km in the core zone were around 30% to 40%, and within a scope of 10 km, were around 80%.