Abstract: After investigating the influence of some additives(i.e.,Li₂O,Na₂O,K₂O,CaF₂) on hot metal dephosphorization in 15 kg vacuum induction furnace,production test in 120 t top and bottom combined blown converter was carried out to smelt the ultra-low phosphorous steel through adding lepidolite ore which contains Li₂O,Na₂O and K₂O during the dephosphorization period.The experiment results of 15 kg vacuum induction furnace show that through adding 15% Li₂O to the dephosphorization slag,the phosphorus mass fraction was decreased from 0.109 4% to 0.003% with a dephosphorization ratio up to 97.3%,and the apparent dephosphorization rate reach to 0.021%/min within 5min since the beginning of dephosphorization.Furthermore,in the production test,the average phosphorus mass fraction and the average dephosphorization ratio of semi-steel are 0.035% and 68.1% with the original phosphorus content in the molten iron charged into converter at 0.109 9%.In addition,the average phosphorus content and the average dephosphorization ratio at the BOF endpoint are 0.005 8% and 94.8%.The corresponding minimum phosphorus content and the maximum of dephosphorization ratio at the BOF endpoint are 0.003% and 97.3%,respectively.