In the present study, removal of oxygen from liquid iron by Ar and (10%-40%) H-2 plasma arc melting have been investigated experimentally. It is shown that the reduction of oxygen content is slight when the plasma gas was argon only. However, the oxygen content of the iron melt decreases sharply when adding hydrogen in plasma gas, and the rate of deoxidization increases with the hydrogen content. The final oxygen content can be as low as 1 ppm after hydrogen plasma arc melting (HPAM) with 40% H-2 in plasma gas. The deoxidization from the iron melt by HPAM was a two-steps process: the fast 1st step and the slow 2nd step. From kinetic analysis, the oxygen removal by HPAM was found to obey a first-order rate law. In the 1st step, the reduction rate of oxygen increases proportionally to the approximately 0.44th power of the hydrogen volume proportion in plasma gas. The deoxidization process can be expressed as the following reaction: [O] + 2H = H2O. The thermodynamic analysis indicates that deoxidization power of atomic H is higher than that of molecular H-2. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.