Abstract: Aiming at local treatment of material surface by plasma, a glow discharge N2 plasma gun to be used in atmosphere was designed to investigate and analyze theoretically its discharge characteristics and jet intensity. As experimental results, the discharging volt-ampere characteristic curve and effect of jet flux on torch's working voltage/current were discussed on their causes, with an analytic curve-fitting equation given. It was found that the working voltage and current is exponentially increasing and decreasing in relation to jet flux, respectively. Furthermore, the jet from the plasma gun is characterized by expanding first then contracting, with a maximum active sectional area found 5 mm distant from torch tip. The optimal intensity gas jet is 0.2 m³/h. The operation mechanism of the plasma gun was thus discussed further to find out the optimal conditions on which the specimen preparation will be available.