Abstract: As to the gas pool coupled activating TIG arc with the outer gas being the mixture of nitrogen and oxygen, Boltzmann plot method was applied to analyze the temperature distributions of the arc plasma and the regularity for change of the arc voltage when they were under different coupling degrees, and then the results were compared with the traditional TIG arc and the gas pool coupled activating TIG arc only using oxygen as the outer gas, respectively. The results show that both the plasma temperature of central zone and the arc voltage of the gas pool coupled activating TIG arc with the outer gas being the mixture of nitrogen and oxygen are higher than those of the TIG arc and gas pool coupled activating TIG arc with oxygen being introduced only. When the coupling degree h is changed from 0 to +2, both the arc plasma temperature of central zone and arc voltage are increased slightly.