This paper focused on numerical and experimental research on mechanical behavior of thick steel plate members. Firstly, the magneto-elastic equipment was used to obtain the MP-σ curve, and the residual stress of thick plate welded joints was measured by using magneto-elastic method. Secondly, based on the ABAQUS finite element code and subroutine DFLUX, the welding procedure on the butt weld of thick steel plates was simulated. The numerical and experimental results show that: 1) the welding longitudinal residual stress is bigger than the transverse residual stress as a whole; 2) the welding longitudinal residual stress along Y axis increases with the increase of plate thickness, especially when the thickness is less than 60 mm. Moreover, coupling temperature field and stress field, and also considering damage accumulation, weld thick plate members under low-cycle loading were analyzed. The result shows that welding residual stress has a big influence on the distribution of accumulative damage under low-cycle loading.