Control of the formation of nonmetallic inclusions and their characterization is the foundation for improving the qualities of steel products, as well as designing new types of steel. In order to produce steel with improved machinability, such as austenitic stainless steel X8CrNiS18-9, is made modification of the chemical composition of nonmetallic inclusions. In this paper, Thermo-Calc phase calculation and SEM studies of the presence and type of inclusions in austenitic stainless steel with the addition of sulphur of the label X8CrNiS18-9 with and without addition of alloying elements Zr and Te, were carried out individually in order to investigate their influence on the shape and chemical composition of the inclusions.