Abstract: The hydrodynamic characteristics of Pulandian bay was studied based on the unstructured numerical model, the influence of different removal elevation of pool stem on water exchange was studied coupling the transport and diffusion model. The result showed: the direction of fluctuations in Pulandian bay was basically the same as that of the shoreline, after the pool stem was removed, the water area would increase by 15% and bay tidal volume would increase by 10%. When the elevation of pool stem was low in plan 1, the flood and dry-out flow was more uniform on intertidal zone; when the pool stem remained too high in plan 2, the flow velocity between the pool stems were large, and the tidal current field was chaotic. Before the project, the water half-exchange time of water in the bay gradually increased from 0 d to 70 d, and above 70 d at the bottom. After the project, the maximum half-exchange time in the bay of plan 1 was reduced to 50 d, and reduced to 60 d in plan 2. The average half-exchange time in the bay was 36.8 days, which dropped to 24.0 days after the implementation of plan 1, and 28.5 days for plan 2, the water quality improvement of plan 1 is 12% higher than plan 2.