Since 1992 when polders began to appear along the coast for aquaculture,a long-term experiment has been carried on to study dynamic variation of salts in the water and bottom mud of the polders as affected by aquaculture in Defang region. Results of the monitoring between 1996 and 2005 show 1)salt concentration in the waterbody decreased from 3.67 to 2.28 g L^-1 in the aquaculture system with river water high in mineralization(Na-Cl>3.5 g L^-1)and rainfall as water sources for replenishment;2)total soluble salts in the pond mud decreased year by year,from 3.22 to 1.06 g kg^-1;and,a significant linear relationship was observed between total soluble salts and Cl^-1 content in pond mud;and 3)an exponential curve model could be used to predict desalinization trend of the mud;and the predicted values of the years to follow are δ₂₀₀₇=0.824 g kg^-1 and δ₂₀₀₉=0.638 g kg^-1,respectively,which may serve as a scientific basis for future reclamation of the polder into farmland.