Effective generation of chemical reactive species in thermal plasmas has been required in the field of material processing and waste treatment. The effect of oxygen injection into argon induction plasmas was investigated by numerical analysis without chemical equilibrium assumptions. Reaction kinetics rates of the dissociation and recombination of oxygen as well as the ionization were taken into account. The transport properties were estimated using higher-order approximation of the Chapman-Enskog method for required accuracy. Oxygen dissociation and heat flux to a torch wall can be controlled by oxygen injection location. Therefore, suitable oxygen injection needs to be chosen according to the application requirement. The present modeling would give more precise information and provide the guidance for the rational design of new material processing with effective reactive gas injection into plasmas.