Precipitation condition and nucleation of Ti2 O3 during solidification of clean steel have been studied. The behavior of Ti2 O3 during solidification as well as possibility of using Ti2 O3 to refine as-cast grains as heterogeneous nucleation sites is discussed. It is shown that Ti2 O3 can be formed provided that the steelmakin9 and solidification process is controlled strictly. And inoculating clean steel with Ti2 O3 is an effective way to refine as-cast grains.