Abstract: To understand inclusions in tire cord steel, the solidification process has been analyzed and the conclusions drawn as follows. Al₂O₃ precipitates earlier during solidification and the growth rate depends on the diffusion of [A1] in molten steel; SiO₂ begins to precipitate when the solidification fraction is 0.44, and the growth rate depends on the diffusion of [O]. The inclusion radius increases with the decrease of cooling rate, the radii of Al₂O₃ and Al₂O₃-SiO₂ inclusions are 2.5 μm and 4.7 μm, respectively, after solidification as the cooling rate is 100 K·min^-1. SiO₂ content increases and Al₂O₃ content decreases during solidification.