The effect of vanadium (V) on the modification of oxide inclusions in steels with different concentra-tions of Mn, Si, and V was determined before and after heat treatment at 1473 K.Changes in the morphology, size, and composition of these inclusions were analyzed.Equilibrium relations between the inclusions and steels at 1873 K and 1473 K were calculated using available thermodynamic data to roughly approximate the stable oxide inclusions in the steels.The results revealed that the concentra-tions of V and Si in the steel are critical for controlling the modification of the inclusions during heat treatment at 1473 K.MnO-SiO2-type oxide inclusions gradually transformed into MnO-V2O3-type or Mn-SiO2- and MnO-V2 O3-type inclusions in low-Si high-V steels heat-treated for 60 min.In addi-tion, the morphology of the inclusions changed from spherical to irregular.A Si-accumulated zone and a V-depleted zone formed close to the interface in the steel matrix.The experimental and calcula-tion results indicated that, during the heat treatment, an interface chemical reaction occurred be-tween the Fe-Mn-Si-V steel and the MnO-SiO2-type oxide inclusion.