ABSTRACT To obtain solid inclusions in LF refining process, the influence of silicon content in steel on compositions of inclusions during LF refining were investigated in Al-killed steel. Influence of silicon on compositions of inclusions was found to be great. The [Ca] content of steel was supplied from the reaction of [Al] and CaO. The [Si] content affected the [Ca] content by the reaction (SiO2) + 2[Ca]→[Si]+2(CaO), and [Ca] was consumed more readily by SiO2 in Si-free steel than in Si-containing steel, as a result, Al2O3 and MgO·Al2O3 inclusions could be obtained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. Moreover, the inclusions were mainly solid Al2O3 with low contents of CaO and MgO when using low-calcium ferrosilicon alloy and adding all low-calcium ferrosilicon alloys required for the steel at the end of LF refining, this ensures high removal efficiency of inclusions in RH degassing.