Calcium peroxide is applied to sediment remediation. Based on laboratory-simulated test, trend of soluble reactive phosphorus (SRP) concentration in overlying was measured after two means of calcium peroxide treatment, mixing and capping. Transformation among different phosphorus fractions in the sediments was studied to analyze the distinguished effect. The results show that SRP concentration in overlying water presents different trend after mixing and capping of calcium peroxide. SRP concentration of the former decreased at first and increased subsequently, while that of the latter kept decreasing and average release velocity of SRP was 6.077 mg/(m2 x d) and -0.879 mg/(m2 x d) respectively. The transformation of phosphorus fractions in the sediments shows that diverse change of iron-bound phosphate are deemed to cause the effect under different adding options of calcium peroxide.