The main objective of the present study is to clarify the effects of gas injection conditions such as gas mixing and gas injection location on the thermofluid characteristics and on the luminary areas of RF induction plasma flow. The gas temperature distibution shows the drastic variations due to the circulation by Lorentz force, the diffusion of mixed gases and complex flow patterns. On the other hand, the dissociation of N_2 or other secondary mixed gases cause the decrease in the temperature and the luminary area.