The morphologies evolution of various types of inclusions in Ti-IF steel were observed by a special depth erosion method,and the formation and evolution process were discussed.The results showed that the main inclusions were FeO·xMnO before Al deoxidization and the ratio of integrated oxygen and free oxygen was in ranged of 0.3 to 0.4.In present study,the main effect factors on the morphologies of Al_2O_3 inclusions were [Al]/[O]_(Free)(soluble aluminum divide free oxygen) and initial free oxygen;cluster Al_2O_3 was formed easily with high free oxygen([O]_(Free)) and low[Al]/[O](blew 3 in present study).Otherwise,the dendritic Al_2O_3 was formed;coral-like Al_2O_3 was the mixture of the dendrite Al_2O_3 and spherical Al_2O_3.Some Al_2O_3·TiO_x inclusions appeared because a high[Ti]concentration region existed around 70TiFe(containing 70 percent titanium) particles after 70TiFe addition.The maximum sizes of Al_2O_3 reached 800μm when 3 min aluminum was added;as the time past,the large size Al_2O_3 decreased significantly;the maximum size of Al_2O_3 was blew 100μm and 50μm in calming sample and tundish sample respectively. The morphologies evolution of various types of inclusions in Ti-IF steel were observed by a special depth erosion method, and the formation and evolution process were discussed. The results showed that the main inclusions were FeO · xMnO before Al deoxidization and the ratio of integrated oxygen and free oxygen was in ranged of 0.3 to 0.4. present study, the main effect factors on the morphologies of Al_2O_3 inclusions were [Al] / [O] _ (Free) (soluble aluminum divide free oxygen) and initial free oxygen; cluster Al 2 O 3 was formed easily with high free oxygen ([O] _ (Free)) and low [Al] / [O] (blew 3 in present study) .therwise, the dendritic Al 2 O 3 was formed; of the dendrite Al_2O_3 and spherical Al_2O_3.Some Al_2O_3 · TiO_x inclusions had a high [Ti] concentration region played around 70TiFe (containing 70 percent titanium) particles after 70TiFe addition. The maximum sizes of Al_2O_3 reached 800μm when 3 min aluminum was added; as the time past, the larg The maximum size of Al 2 O 3 was blew 100 μm and 50 μm in calming sample and tundish sample respectively.