A welding finite element model for TA15 titanium alloy panel structure is developed. The influence of welding sequence on the panel distortion is investigated by using thermo-elastic-plastic finite element method. The double ellipsoid heat source models which are suitable for the site TIG penetration welding process are established through comparing the weld cross-section and the residual stress of calculation and experiment. Furthermore

the distortion behaviors of the panel structure in different welding sequences are simulated. The results show that the distortion of the middle part of thin plate is severewhen the welding starts from one side

and the maximum distortion is 3.9mm. The distortion of the thin plates is improved effectively by using the symmetrical welding sequence.