Abstract:A mathematical model of Luoyuan Bay was established based on Mike21 for analysis of the hydrodynamic characteristics and flow field in Luoyuan Bay, and the model parameters were calibrated, with the Smagorinsky coefficient in the bay determined as 0.28, the roughness ranged from 0.024 to 0.035, and the wind drag coefficient ranged from 0.001 0 to 0.001 5. Then, the model was used to calculate the water body exchange period and tidal prism in Luoyuan Bay, and the results showed that the flow velocity in Luoyuan Bay varied from 0.20 to 1.56 m/s for rising and falling tides, the hydrodynamic conditions were strong at the bay mouth and Kemen Channel, and poor at the north bank and northwest corner of Luoyuan Bay, and the influence of tides outside the bay on the north bank was lower than that on the south bank. The half-exchange period of water body in Luoyuan Bay was about 15 d, and the average exchange rates of water body in Luoyuan Bay were 48.5%, 69.3%, 78.8% and 85.5% after 15 d, 30 d, 45 d , and 60 d, respectively. In autumn, the average tidal prism in Luoyuan Bay was 5.73 × 10^8m3, and those of spring tide and neap tide were 7.07 × 10^8m3 and 4.40 × 10^8 m3, respectively. It is suggested that in the process of controlling the flux of pollution sources into the sea, the discharge of pollutants into the sea from the northwest corner of Luoyuan Bay should be reasonably controlled with consideration of the hydrodynamic conditions of the sea area.