Key problems for the control of inclusions in an SiMn-killed stainless steel were summarized in the current chapter, including the cleanliness control of ferrosilicon alloys, slag refining technology, calcium treatment of the molten steel, and composition transformation of inclusions in the solid steel during heating. The ferrosilicon containing low aluminum and low calcium should be used in order to lower the Al2O3 percentage in inclusion. The refining slag with a low basicity and a low Al2O3 content was suggested to reduce the content of MgO·Al2O3 spinel in inclusions. It was found that inclusions in the stainless steel could react with the Cr element in steel matrix during the heating of the solid steel, which transformed MnO-SiO2 inclusions into MnO-Cr2O3 ones. Calcium treatment should hardly be used during the production of SiMn-killed stainless steels.