The non-equilibrium reflux reaction behavior of phosphorus was studied by using the AR chemical reagents and changing the initial condition of basicity, FeO, MgO and Al2O3. Due to the increase of viscosity, the dephosphorization slag with high basicity inhibits the full contact of slag and iron, which lead to the low reaction rate in early stage. However, since the high basicity improves the activity coefficient of CaO, the dephosphorization rate and phosphorus capacity goes up in late reaction stage. FeO promotes the increase of reaction rate in early dephosphorization stage. But the polarization force of Fe2+ is stronger than Ca2+, which hinders the reaction between phosphate ion and CaO and reduces the stability of PO43-. Thus, high content of FeO will adversely impact on dephosphorization reaction. In addition, MgO has a promoting effect to the dephosphorization, whereas Al2O3 has a negative influence.