Abstract: The reoxidation mechanisms of IF steel containing Al and Ti by reducible oxides in the slag were analyzed.A model of predicting total oxygen in the molten steel was established based on the reoxidation mechanisms.It was found that two different reaction mechanisms existed when(FeO) and(MnO) in the slag reoxidated the molten steel.Reoxidation occurred at the slag/steel interface when mass transfer of reducible oxides in the slag dominated the reaction,and the oxidability of the slag exponentially declined with prolonging time.When mass transfer of de-oxidative elements in the molten steel dominated the reaction,reoxidation carried out in the molt steel.A specific formula between the oxidability of the slag and time was obtained by regressing the data from a steelmaking plant.