Abstract: According to TIG welding character of Invar alloy and 45 carbon steel, geometric model was founded and double ellipsoid heat source model was selected as welding heat source.Temperature fields of base materials with different thickness were simulated using ANSYS, and coupled field of temperature and stress was realized to simulate the residual stress distribution.Experiments under different thickness and welding parameters were carried out and distortion of base materials with different position was detected.Thus comparison between simulation results and experimental results can be carried out.The results show, welded joint with well metallurgy and penetration of invar alloys can be obtained using welding parameters of 132 A, 17.1 V, 4 mm/s and 1.88 mm thickness;and the results of temperature fields simulated by finite element method accords well with experiment results.