The phosphate removal mechanisms of Calcite were investigated with the tests of Xray diffraction (XRD) analysis, transmission electron microscope (TEM) measurement, fourier transform infrared spectroscopy (FTIR) analysis , specific surface area by BrunauerEmmettTeller(BET) method and pole size distribution by BarrettJoynerHalenda(BJH) method. The main influencing factors on phosphate removal were investigated and the removal mechanism was approved. It was shown that phosphate removal efficiency was significantly influenced by reaction time, temperature, pH value and dosage of calcite. And with BET, BJH and TEM tests, no porous materials, less than 16.0 m2/g for the specific surface area and below 0.085 cm3/g for total pore volume, were found during the reaction process so as to prove that absorption was not the main way of phosphate removal. And based on XRD and FTIR tests, it was found that chemical precipitation was the main way of phosphate removal which contained two steps: the formation of CaHPO4·2H2O(DCPD) and its transformation to ACP, and the controlling step was DCPD’s transformation to ACP.