Abstract: As a semi-closed bay, many reclamation works have been implemented in Zhanjiang bay since the year 2003， so that the water areas have been reduced by 3.2%. The reclamation works must have accumulative influences upon the flow field, tidal prism, water exchange and even the hydrodynamic environments. A two-dimension water quality numerical model is adopted in simulating the variation of tidal dynamics based on verification progress of the measured data concerning tide and tidal current. The changes in topography and coastline of 2003, 2007, 2012 and 2015 are simulated to compare the flow distribution and the feature point velocity variation, and calculate the changes of the tidal prism and the water exchange in the Zhanjiang bay. The analysis results indicate that the reclamation works have great impacts on the waters near the engineering areas, and less on the main channel. The tidal prism in the Zhanjiang bay decreases with the decrease of the water area, and in 2015 it decreases by 3.4% as compared with 2003. The reclamation works in the deep water, especially in the main current, which result in a bigger hydrodynamic environment change and tidal volume change, should be paid more attention to. The long-term reclamation construction in the Zhanjiang bay has obvious impacts on the water exchange near the engineering areas, and the Baoman harbor, which is located in the deep water, especially in the main current， has resulted in great changes of water exchange. The reclamation works should be taken into account in combination with the pollutant control schemes to implement in the long-term shoreline planning in the future.