Abstract: A model was established to evaluats the three dimensional transient temperature field for Tungsten Inert Gas(TIG) welding by using the Finite Element Method(FEM).ln this model,the dependence of the materials' thermal physical properties on teperature and the heat dissipation fron the surface of materials were considered,and the concept of heat enthalpy was utiliged.The temperature profile in the heat Affcted zone(HAZ) for TIG welding was calculated with this model.the results shown that the theoretical predictions are in good agreement with the experimental measurements.