Abstract: Aiming at the assembly deviation caused by butt welding of flexible parts, on the basis of completing the “N-2-1” flexible positioning, the influence coefficient method was used to model the assembly deviation of flexible parts and analyze the assembly deviation caused by welding. Secondly, the finite element simulation is carried out by Ansys to study the influence of the number of solder joints and welding heat on the assembly deviation. Finally, a case study is carried out with the welding of body door frame. The method can be applied to the multi-solder joint assembly deviation analysis of flexible parts considering the influence of welding heat.