In this paper, the behavior of phosphorus transfer from CaO-SiO2-FetO-P2O5 slags to 2CaO·SiO2 (C2S) particles is investigated. The reaction between C2S particles and the slag saturated C2S is conducted at 1 500 ℃ in laboratory. Ingredients at different positions on the interface between C2S particles and the slag are observed and analyzed by SEM/EDS and the phosphorous transfer behavior is discussed. The result shows that C2S particles react with the particles surrounded molten slag in the solid-liquid two phase zone and forms the n·2CaO·SiO2-3CaO·P2O5 (nC2S-C3P) solid solution. With the reaction time progressing, the thickness of nC2S-C3P solid solution layer increases. In the direction to the inside of C2S particles, the phosphorus content in the nC2S-C3P layer decreases. Knowing the behavior of phosphorus transfer from CaO-SiO2-FetO-P2O5 slags to C2S phase is helpful to study the formation mechanism of nC2S-C3P in the slags.