Abstract: The big changes in tidal level have a great impact on nearshore landscape and hydrophilicity. For this reason， we often construct gates at the bay mouth to control the tidal level changes of the bay. As results， the hydrodynamic and water exchange capability in the bay can be affected. The problems can be improved by setting the landscape water level. However， this will decrease the hydrodynamic and water exchange conditions in the bay. Taken Maluan Bay as an example， the tidal current mathematical model is used to simulate and study the relationship of numbers of gate openings， opening positions， different landscape water levels at the bay mouth and the hydrodynamic and water exchange in the bay. It shows that largescale circulation is formed in the bay by regulating the gate operation at the bay mouth to enhance the water exchange efficiency. Here， suggestions are made on the control of landscape water level and on the gate operation mode of Maluan Bay. Hence it may effectively solve the problem of low water exchange efficiency caused by tidal range decrease in the bay．