To understand inclusions in tire cord steel, the solidification process has been analyzed and the conclusions drawn as follows. Al
2O
3 precipitates earlier during solidification and the growth rate depends on the diffusion of [A1] in molten steel; SiO
2 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 Al
2O
3 and Al
2O
3-SiO
2 inclusions are 2.5 μm and 4.7 μm, respectively, after solidification as the cooling rate is 100 K·min
-1. SiO
2 content increases and Al
2O
3 content decreases during solidification.