Abstract: In order to obtain high manufacturing precision, CFETR window collar ring is welded into a integrity by EBW which has features of higher precision, smaller deformation than other fusion welding methods. According to the inherent strain theory, the inherent strain of EBW welding is calculated, then the result is imported into software. Simulation of welding deformation of four kinds of collar ring welding program without clamp is to determine the optimal welding sequence and fixture constraints, and then the simulation of welding deformation of four kinds of collar ring welding program with clamp were done. The results show that window collar with a different welding sequence results in different welding deformation. Fixture constraint can effectively reduce welding deformation. The results provide a reference for the actual welding process of window collar ring.