MnS inclusions in steels usually have many kinds of morphology. It is difficult to accurately obtain the characteristics of inclusions by two-dimensional observation due to the complex morphology of sulphides in steel, especially the type II MnS inclusions. In this study, the three-dimensional morphology of sulphide in high sulphur steel was investigated by using non-aqueous solution electrolytic etching. Inclusions with a circle and ellipse morphology in two-dimension show more complex morphology in three-dimension. The differences in the distribution, size, shape of sulphides between the two-dimensional and three-dimensional state in the high sulphur steel were studied. Compared with the statistical results of inclusions in two-dimension, the diameter and area in three-dimension are larger than those in two-dimension. Moreover, the proportional function between the size of inclusion in two-dimension and that in three-dimension is proposed. [ABSTRACT FROM AUTHOR]