Abstract: This paper mainly related to the feasibility and experimental research on predephosphorization of semi-steel with LF refining final slag. The experimental results showed that LF refining final slag could be used for predephosphorization of semi-steel，and the dephosphorization effect was good after adding appropriate amount of dolomite. The minimum，maximum，and average dephosphorization rates were 61.31%，71.76%，and 65.03%，respectively，which were higher than that of the contrast test with 55.36% dephosphorization rate by 10.75%，29.62% and 17.47%，respectively. The optimum process parameters in this work were 1 700 mm top lance height，18 500 m3/h oxygen flow rate，360 s oxygen blowing time，2.0 t LF refining final slag addition，1.0 t dolomite addition，and 300—400m3/h bottom blowing gas flow rate.

Key words: LF refining final slag, predephosphorization of semi-steel, feasibility, dephosphorization rate