B 2 O 3 was added to tire cord steel during refining in a carbon tube furnace. The influence of boron on the deformability of oxide inclusions was studied by metallographic and scanning electron microscope (SEM) observations. The melting points of boron-bearing compound oxide inclusions were calculated using Factsage software. The results showed that the main inclusion was a boron-bearing compound oxide and the deformation properties of the inclusions were clearly improved by adding B 2 O 3 . As the boron content was increased from 0.0046% to 0.039%, the proportion of long strip type inclusions changed slightly and the number of inclusions decreased. The low-melting point areas of the MnO-SiO 2 -Al 2 O 3 and CaO-SiO 2 -Al 2 O 3 ternary system increased with the addition of B 2 O 3 . Moreover, the area increased with the increase of B 2 O 3 content. Clear improvements in the deformation ability of the inclusions occurred when the B 2 O 3 mass percent rose to 5% in the CaO-SiO 2 -Al 2 O 3 inclusion system and to 10% in the MnO-SiO 2 -Al 2 O 3 inclusion system.