[en] An analysis of deformation characteristics and residual stress of the welding structural materials is indispensable for a design and fabrication of welding parts of nuclear structural materials such as a pressure vessel, a reactor head, nozzle and piping, etc.,). It has been reported in a foreign reactor that the residual welding stress caused a fatal problem of PWSCC to the nuclear structural materials. For this reason, in this study, we carried out a basic study on the development of a residual welding stress measuring technology with high reliability and precision. For example, the status of the dissimilar metal welding parts such as a nozzle-safe end and a pipe-safe end for the domestic nuclear power plants and the PWSC cases of welding structural components (RVHP, BMI) and dissimilar metal welding parts including the proposed measures for them were reviewed. Also, a measurement of residual welding stress by Hole drilling/X-ray diffraction methods and an establishment of their data base by using SA 508 low alloy and Alloy 52 filler metal, and a qualitative residual welding stress measurement technology using a standard test specimen under an in-situ tensile loading l were studied. The experimental data and technology on the residual stresses of welding structural materials of nuclear power plants would be used for an improvement of the residual stress measuring system in Hanaro. Furthermore, they can contribute to obtain the reliability for the welding parts of commercial up-coming nuclear power plants as well as can be applied to the other industries such as an aviation, shipbuilding and space. They also could contribute to build-up a highly reliable residual stress measuring technology for the weld parts of commercial up-coming nuclear power plants and thereby to provide the design and fabrication industries with an optimum welding procedure