The purpose of this research was development of the model for temperature field analysis under friction stir welding. Mathematical asymmetric heat source model was studied, its capability in comparison with experimental results was proved. Two-dimensional temperature field distribution was studied using Ansys software. Necessary experimental results were obtained by means of welding experiment where the 400x125x2 mm plates were welded. The temperature was measured using thermocouples. Aluminum alloy EN AW 6082 T6 was chosen as a material for workpieces. The simulation model is tasted with experimental result. The results of the simulation are in good agreement with experimental results. Influence of clamps and back plate during friction stir welding was found.