This paper describes numerical analysis of a supersonic O 2 -jet impingement on carbon-contained liquid iron under vacuum circumstances. The gas phase is assumed to be composed of O 2 , CO, CO 2 , O and C. Since gas temperature is elevated over 1 000 K in the vicinity of the surface of liquid iron, high-temperature gas effects, namely vibrational energy excitation and dissociation, are included in the analysis. Therefore, the flow field is expressed by Navier-Stokes equations consisting of mass conservation, momentum, overall energy, vibrational energy and species mass conservation equations. Furthermore, surface reactions for O 2 -C and O-C encounters are included in surface boundary conditions. Cavity geometry is determined from the balance of pressure, shear stress, surface tension and liquid buoyancy. Based on the numerical results, sensitivity of mass fraction for each species to the probability of surface reaction is discussed. In addition, the effect of the surface reactions on the cavity geometry is clarified.KEY WORDS: jet impingement; supersonic jet; surface reaction; thermochemical nonequilibrium.