<p>Due to the relative high content of aluminum, the aluminum-contained inclusions are apt to be precipitated during the continuous casting process of high-manganese non-magnetic steel and has great effects on the final property of steel. In this paper, the characteristics and distribution of inclusions in thickness direction of high-manganese non-magnetic steel slab were investigated by means of Particle-X automatic scanning electron microscope, SEM-EDS, and Thermo-Calc thermodynamic calculation. The results show that the high-manganese non-magnetic steel mainly includes AlN, AlN+Al₂O₃, Al₂O₃, MnS, AlN+MgS, and MgS+MgO. The total proportion of AlN, AlN+Al₂O₃, and Al₂O₃ is as high as 97&#xa0;pct. From the surface to the center of slab, the number of AlN inclusions decreases first and then increases slightly in the central equiaxed crystal zone, but the number of AlN+Al₂O₃ inclusions shows a slight increase in the mixed zone. The average size of AlN and AlN+Al₂O₃ inclusions increased first and then decreased from the surface to the center of slab. The average size of AlN inclusions reaches a maximum of 4.4 <i>μ</i>m in the columnar zone, but the average size of AlN+Al₂O₃ inclusions also reaches a peak of 6.8 <i>μ</i>m in the mixed zone. During the continuous casting process of high-manganese non-magnetic steel, the dispersed Al₂O₃ inclusions in the molten steel can provide the nucleation sites for the precipitation of AlN and promote the AlN+Al₂O₃ composite inclusions form with the core of Al₂O₃ wrapped by AlN. The AlN+Al₂O₃ composite inclusions are pushed forward by the columnar crystals from the slab surface and blocked by the equiaxed crystal formation at front of columnar crystals, where the columnar-to-equiaxed crystals transition (CET) occurs. Thus, both the number and average size of AlN+Al₂O₃ inclusions show an increase trend in the mixed zone.</p>