Abstract: To provide a theoretic foundation for industrial plasma applications, in locally thermodynamic equilibrium, the beam current from a nitrogen plasma gun was simulated in atmosphere, through solving the RNG k-Ε equation, and difference grid. The shape of beam current was thus got and it was basically in conformity to that measured in simulation. The temperature field of the plasma beam current was calculated on the condition of different gas flux, with the shape of beam current found through plotting its boundary at 600 K. The results showed that when the gas flux F<0.8 m³/h, the size of beam current decreases with decreasing gas flux, and when F>0.8 m³/h, the size distribution of beam current tends to be stable. If so, a better plasma source is available to plasma applications. It was verified the best size range of beam current for plasma applications is 7-8 mm which is also the maximum one.