The hydrodynamic influence due to large scale suspended aquaculture farm off Gouqi Island, China, was studied, using a 3-dimensional numerical Model (Estuarine Coastal Ocean Model, semi-implicit, Ecom-si). A momentum sink method was used in the model to represent the retarding effect caused by the resistance of aquaculture sleeves. The numerical model was then validated with observed data of tides and flow speed. The model results showed that the existence of suspended mussel sleeves in water reduced the flow speeds, the surfaces currents were reduced by about 80%. At the same time, it increased the tidal current velocity at the edge of the farm throughout the water column.The simulation results of Lagrange particle tracking module showed that it took about 600 hours for the particles to reach the settlement rate of 36.79% (e^-1) when the detritus particles were in suspension state. The particles were distributed in the region of 9.0-10.5 km away from the center of the farm zone without the retarding effect, and that were distributed in the region of 7.5-8.5 km away from the farm center with the retarding effect. When w was greater than 0 m/s, there was little difference between 3 kinds of detritus settlement velocities, and the particle settlement rate reached 99% in about 80 hours. The particle settlement area was within a range of 10.0-13.5 km from the center of the culture area without retarding effect and the particle settlement area was within a range of 6.8-12.0 km from the farm area with the retarding effect. The settlement range of the released particles during the spring tide showed a wider ecological radiation range of detritus than neap tides released. The tidal residual current was the main dynamic factor that determined the detritus transport path and settlement position without considering the drive of wind stress.