The electro-slag remelting (ESR) process offers numerous advantages over other steel-making methods due to the exceptional metallurgical reaction conditions and unique crystallization mode [1,2] . However, as ESR is typically performed directly in the atmosphere, the oxygen content in the ESR steel is significantly higher than that of vacuum arc remelting [3,4] . Consequently, it is crucial to regulate the oxygen content in the electro-slag remelting steel.Slag plays a profound role in ESR process. During the remelting process, the slag exhibits relatively high electric resistance, resulting in most of the electric energy being converted into heat energy within the slag pool. As a result, the slag remains at a high temperature and is able to continuously melt the consumable electrode. In general, FeO, Cr 2 O 3 , MnO and SiO 2 are considered unstable oxides in slags. The metal droplet is in full contact with the slags during ESR as it passes through the slag pool, causing