Abstract: In order to improve the cleanliness of container steel for the compact strip production (CSP) production line of Wuhan Iron and Steel Corporation,the effect of slag compositions,argon blowing and calcium treatment on T[O] and inclusions was studied by industrial trials. The results show that increasing the ratio of (CaO + MgO)/SiO₂ is beneficial to decreasing T[O]in molten steel., but the ratio of (CaO + MgO)/Al₂O₃ should be considered. The increase of argon blowing time before and after calcium treatment can improve the cleanliness of molten steel obviously. The suitable ratios of (CaO + MgO)/SiO₂ and (CaO + MgO)/Al₂O₃ in the slag are not only beneficial to improving the cleanliness of molten steel but also forming the low melting temperature inclusions of CaO-MgOAl₂O₃ type. Based on thermodynamic data,a thermodynamic calculation model for the equilibrium of[Ca]and[Al]was given when liquid calcium-aluminate formed in actual production.