Abstract: In this paper, the finite element (FE) analysis of TIG welding deformation on the sidewall-flange structure of rocket storage tank was carried out. The FE model of TIG welding of sidewall-flange structure of storage tank for 2A14 aluminum alloy was established. The double ellipsoid model was used to simulate the welding heat input of saddle-shaped weld, which was verified by temperature test results and weld macro morphology during welding. The influence of welding starting position and welding sequence on welding deformation of key parts (welding seam and seal groove) was emphatically investigated. The simulation results showed that the deformation was mainly concentrated in the weld zone, while the deformation of the seal groove was relatively small. The welding deformation distribution of weld seam and sealing groove was similar, while the deformation peak was occurred at the point B (B'). Besides, compared to changing the welding starting point, the effect of changing welding sequence on welding deformation was more significant. The optimization results of the welding sequence of sidewall-flange structure of storage tank showed that the welding deformation distribution was more uniform under the cover reverse welding, i.e., scheme 4, which was able to achieve minimum deformation for the weld and sealing groove structure. In that case, the maximum deformation of the weld was 1.022 mm and the maximum deformation of the sealing groove was 0.505 mm.