Abstract: Objective The aim is to investigate influence of surface state on the local repair welding quality of sealing surface of pressure vessel. Methods Numerical simulation and experimental verification methods are used to study deformation of sealing surface after local repair welding under concave state and plane state, and penetration testing is used to analyze weld quality under different surface states after welding. Results The results show that under the same welding process, when sealing surface is local repair welded with plane surface to be welded, there is less deformation after welding. However, wetting angle is large and penetration testing is prone to exceeding the standard display. After removal of simulating defect, the surface to be welded with circular arc transition concave has good surface quality after welding, and there is no linear or circular display in penetration testing. However, the deformation after welding is relatively large, which is not conducive to subsequent surface processing. Conclusion For the local repair welding of sealing surface, defects should be removed with the minimum amount of processing, and the surface to be welded should be processed into an appropriate circular arc shape, which can improve the quality of weld formation while controlling welding deformation.