Abstract: The formation and transformation of non-metallic globular inclusions (Type-D inclusions) in bearing steel production were studied. There were different kinds of Type-D inclusions in the commercial specimens of bearing steel from SEM inspection. Al content had important effect on the inclusion formation in the experiment of an induction furnace. A great amount of MgO·Al₂O₃ formed with high Al deoxidation in MgO crucible melting. With high content of Ca, the inclusions of MgO·Al₂O₃ spinel will become calcium-aluminates entirely. The results show that the contents of Ca, Mg and Al in liquid steel have important effect on the formation of Dtype inclusions. It is tested in the experiment of bearing steel production that Type-D inclusions can be improved by specific slag modification and composition optimization.