Abstract: Objectives To evaluate the longitudinal ultimate strength of the hull girder more accurately and obtain its collapse process. Methods The bulk carrier was modeled finely by the nonlinear finite element software ABAQUS, and the effects of slight, average, and severe welding initial deformation and average welding residual stress on the ultimate strength of the hull girder under hogging and sagging bending moments were fully considered. Results The calculation results show that the hull girder's ultimate strength and bending stiffness decrease gradually with the increase of the initial deformation amplitude. The severe welding initial deformation makes the ultimate strength of the bulk carrier decrease by 14.25 %, and the bulk carrier's ultimate strength decreases by up to 8.22% under the effect of welding residual stress individually. The combined effect of welding initial deformation and residual stress on the hull girder's ultimate strength is not a linear combination of the effects of the two initial imperfections individually. Conclusions The combined effect of welding initial deformation and residual stress on hull girders' ultimate strength should be considered more carefully in the research on the ultimate strength of hull girders.