Abstract: An ingot specimen was obtained by the process of adding Al₂O₃ nano-particle to molten industrial pure iron. The existent state and chemical components of nonmetallic inclusions in the metal-phase sample were investigated by SEM and EDS. Nonmetallic inclusions were extracted from the ingot by the electrolytic method in nonaqueous solution, and SEM and EDS were used to study their characteristics, such as morphology, size, and chemical components. The results showed that additive Al₂O₃ nano-partlcle could be stabilized and combine with microelements, such as Mn and S to form complex inclusions, whose size is about 5-10 μm. Al₂O₃ nanoparticle existed usually in the interior of complex inclusions. The phenomena of reuniting and agglomeration of Al₂O₃ nano-particle was rare. The thermodynamic stability and probability of reuniting and agglomerating of Al₂O₃ nano-particle were also analyzed in molten pure iron.