Abstract: The residual aluminum content has a great influence upon CrNiMoV steel properties and the optimal content is about 0.010%. The aluminum control during the ESR process has been investigated in this paper. All experiments were car ried out in a 20 kg ESR furnace. The results show that when a 60%CaF₂-30%Al₂O₃-5%SiO₂-5%CaO slag system and proper deoxidizing schedule is used, a reasonable ingot with optimal aluminum contents can be obtained. Silicon and magnesium contents are approximately the same with those in the electrode.