Abstract: N₂-Ar protecting tungsten inert gas(TIG)welding arc was chosen as the studied object. A mathematic model was developed according to the theory of magnetic fluid dynamics.TIG welding arc was numerically analyzed based on this 2D, static and axisymmetric model with ANSYS software and the temperature and velocity profiles of the 50%N₂+Ar protecting arc have been simulated. And the difference of the temperature, pressure and velocity of the arc between 50%N₂+Ar protecting arc and Ar protecting arc has been obtained. The results show that the temperature, pressure and velocity of the arc could rise adding N₂ as protesting gas and higher energy density arc can be got.