Abstract: Based on an unstructured grid, finite-volume coastal ocean model, numerical simulation model of tide and tidal current in the Pulandian bay is built.Based on a well-verified tidal flow mathematical model, the Pulandian bay is divieled into six areas, the dissolved conservative materials are used as tracers, an advection-diffusion water exchange numerical model is established.The water exchange ability of each area is studied.The results show that, there are great differences in water change abilities of different areas because of large topography differences of different areas in the Pulandian bay, of which, the horizontal distribution is extremely uneven for the exchange capacity of water resources in the Pulandian bay.Among the six regions of the Pulandian bay, water exchange in Region A (the mouth of the bay) is the fastest, which has an exchange rate of 45% in 10 d, while the slowest Region is F.The water exchange rate is only 14%.The reason for relatively great difference in regional exchange rate in the Pulandian bay is comparatively large regional difference in the exchange control mechanism.