Abstract: To verify the hypothesis that forms of bioactive phosphorus restricting the primary production in sediments can be influenced by exogenous calcium ions, sediments are exposed to calcium ions with different concentrations for 30 days and the difference of forms of bioactive phosphorus in sediments is analyzed. Moreover, the sediments are aerated during the experiments. If the concentration of exogenous calcium ion is 0, 50, 200 and 500 mg/L, the Ex-P content in surface sediments is 0.08±0.02, 0.05±0.00, 0.05±0.01 and 0.06±0.01 μmol/g, respectively. The Ex-P content in surface sediment exposed to exogenous calcium ion with concentration 50 mg/L is less than that in sediment exposed to exogenous calcium ion with concentration 0 mg/L (P< 0.05). Under the same concentration of exogenous calcium ions, the IP content in surface sediments is 0.37±0.10, 0.46±0.16, 0.41±0.06 and 0.69±0.05 μmol/g, respectively. The IP content in surface sediment exposed to exogenous calcium ion with concentration 0 mg/L is lesser than that in sediment exposed to exogenous calcium ion with concentration 500 mg/L (P< 0.05). Nevertheless, the Ex-P or IP content in bottom sediments is not influenced by exogenous calcium ions. Thus, the content of bioactive phosphorus can be influenced by exogenous calcium ions, and there are double threshold effects of exogenous calcium ions on Ex-P content in surface sediments. Moreover, the phosphorus in water body can be transformed into slow-release phosphorus in sediments by exogenous calcium ions.