The effect of heat treatment on residual stress after welding is enormous. For the purpose of analysis of influence law,the welding assembly residual stress subjected to different heat treatment processes are simulated by Sysweld numerical simulation software.It’s composed of tube plate and the annular support plate from the passive residual heat removal system heat-exchanger. Meanwhile,the simulated calculated stress value is compared with the blind hole test stress value,and its mechanical properties are verified by simulation test. The results show that the welding residual stress of the butt weld of the tube plate and annular support plate reduces to the lowest value when it is subjected to stress relief heat treatment at 595 ℃/1.25 h. The minimum stress value is kept constant and the simulated calculated stress value is equivalent to the actually measured stress value level,when the holding time is extended. And the simulated test results also prove that the mechanical properties are at the same level when performing the heat treatment according to different standards.