About 80 kg low carbon steel was refined in a multifunction ladle furnace (AC-LF) with alternating current supplying. The argon-hydrogen gas mixtures were injected into the electric arc zone through one hollow graphite electrode. The flow rate of the gas mixtures was 3 m3/h. Results of the tests and the calculation based on the plasma local equilibrium thermodynamics and metallurgical thermodynamics theories show that, when the argon-hydrogen gas mixtures are injected into the electric arc zone, the carburetion rate is 4.7×10-6 per minute for the steel heated by conventional AC-LF, which is 1.26 and 1.51 times of the heats blown 90%Ar-10%H2 and 80%Ar-20%H2, respectively. The carburetion rate is reduced by 20% at least when argon-hydrogen gas mixtures are blown into the furnace. When H2 content in the gas mixtures reached 20% from 0, the decarburization rate increased but the total reaction rate decreases by 1.59×10-6 per minute.