Abstract: The converter dephosphorization process takes the advantages of capacious furnace，which enables the rapid and efficient dephosphorization with low slag basicity in the early stage of converter steelmaking. The recycling of decarburization slag can also reduce the consumption of lime and other auxiliary materials and the amount of slag emission. Under the conditions of low basicity and low temperature，the low temperature is beneficial to dephosphorization in thermodynamics. But too low temperature will result in the high slag viscosity，which affect the kinetic conditions and make it difficult to pour the slag. The dephosphorization effect is better when the basicity is properly increased. With the increase of FeO content in slag，the dephosphorization ratio first increases and then decreases. The solid and liquid phase coexist in the dephosphorization slag，and the solid solution of Prich phase has good phosphorus enrichment ability. Owing to the complete separation of slag and hot metal after dephosphorization，the duplex process can effectively improve the dephosphorization ratio and is suitable for the production of ultralow phosphorus steel. However，because the process requires two converters，the utilization efficiency of converter is low and the heat loss of intermediate tapping is large. The double slag process only needs one converter，and the cleanliness of molten steel is high，which is an important development direction of converter dephosphorization.