Abstract: The interaction between Mn-bearing slag and steel during direct alloying with manganese ore is studied in presernt paper. Basicity and[Si] and/or[C] content are the main factors influencing the reaction. When using FeSi and SiC as reducing agents, the reduction rate of MnO is in 10^-5 Mn/s·cm² order. But the dessolving process of SiC has some effects on the reduction. After about 10 to 15 minutes,[Mn] tends to be stable. The rate order of SiC-MnO reaction is first order, then increases somewhat.