By analysis on steelmaking data of 150t BOF 3000 heats with 10% 〜17% FeO in slag

slag melting point less than 1450°C and viscosity 1.0 ~1.2 P

it is obtained the effect of BOF index of oxidation of slag (IOS) and slag optical basicity Λ

x

on slag-steel phosphor partition ratio. In order to improve the dephosphorizing capacity

in BOF steelmaking model the dynamic amount of lime addition is set to promote the optical basicity Λ

x

of end slag near to aim Λ

x

=0. 7 ±0. 01 with slag ingredient near to 2CaO·SiO

2

phase； and in steelmaking model

by priority selecting the aim hot metal reduction index Rli 5. 8 ~ 6. 6

setting the aim oxygen blowing index OMI 1.05 ~ 1.20

and optimizing the index of oxidation of slag IOS bing 10 ~ 15

the iron loss decreases and the dephosphorization effect is ensured.