Abstract: The theoretical background of calculating sulphide capacity by the KTH model and the method of calculating sulphur partition ratio were introduced. Some parameters that affect the sulphur partition ratio were studied. The result showed that (1) the sulphur partition ratio increased with the increase of %C, %Al and decreased with the increase in temperature; and (2) the sulphide capacity increased with the increase in temperature and decreased with the increase of % Al₂O₃/% CaO in the slag.