Abstract: A control technology of magnesium content in CrNiMoV steel during ESR process has been studied. The experimental results show that the optimum slag (mass frictom) constitution is 62%CaF₂-10%Al₂O₃-12%CaO-16 %MgO and the amount of deoxidiser added is 1. 5g CaSi per kilogram of liquid steel. The higher magnesium content of electrode and higher remelting current is beneficial for obtaining remelting ingots with predicted magnesium content.