The removal of phosphorus from micro-polluted lakes, reservoirs and other water bodies has become a main direction of water quality research. Phosphorus is a key factor in the eutrophication of water bodies and can easily lead to eutrophication and algae bloom even at low concentrations. Many phosphorus removal methods are not effective in removing low concentrations of phosphorus. Therefore, out of 22 natural minerals, volcanic ash materials and water-hardened materials, we selected sulfoaluminate cement (code R-SAC 42.5, abbreviated R), which can effectively remove low concentrations of phosphorus. This material is flocculated in neutral and slightly acidic solution. Based on the adsorption kinetics, isothermal adsorption curves, and SEM and XRD analyses, we investigated the mechanism of phosphorus removal from micro-polluted water, the effects of environmental conditions (pH, temperature, light, perturbation and dissolved oxygen) on the re-solubilization of phosphate already adsorbed by the R floc, and the effect of R on phosphorus in real micro-polluted water. The results showed that under neutral conditions, the R floc could completely remove phosphate within 0.5 min. Phosphate (0.10 mg/L) could be completely removed by 0.10 g/L R floc. Preliminary analysis showed that the removal of phosphorus was due to chemisorption between the R floc and phosphate, and the initial stage of adsorption could be described by the Langmuir isotherm. SEM and XRD analyses showed that phosphate was mainly adsorbed on the tricalcium silicate surface in R. The flocculated R increased phosphate adsorption through the net capture, compression, and precipitation of ions in solution. More than 90% of the phosphate could be removed at pH 5.0-8.0. Light, temperature, and dissolved oxygen did not affect the phosphate removal. Disturbance resulted in partial desorption of phosphate, but the phosphate concentration remained below 0.05 mg/L. The application to a real micro-polluted lake/reservoir showed that flocculated R can be used to control phosphate levels in lakes and reservoirs by removing phosphate, trapping the suspended matter and preventing from eutrophication and algae bloom in the water.