The amount, composition, morphology, size, and spatial distribution of inclusions in the steel have an important effect on properties and the surface quality of stainless steels. The appearance of the stainless steel product was seriously influenced by inclusions-related defects, such as line defects and spot defects, after the polishing of steel plates. Firstly, it was necessary to remove more inclusions in the steel to improve the cleanliness of the steel. The low basicity slag could lower Al2O3 and MgO contents in inclusions. The deoxidation curve and stability diagram of inclusions in stainless steels were calculated to predict the formation of inclusions. The evolution of inclusions during the entire production process of Si-Mn-killed austenitic stainless steels was investigated.