The bi-moment is a key factor in calculating the warping normal stress induced by restrained torsion in container ships. At present, bi-moment evaluation is mainly carried out using the transfer matrix method or one-dimensional finite element methods based on thin-walled structural mechanics, which involves relatively complex computational procedures. In this study, the CCS software for combined bending moment and longitudinal strength assessment of large-opening ships was employed to calculate the bi-moment for twelve container ships. The longitudinal distributions of torque and bi-moment were systematically analyzed for single-island and double-island configurations. Distinct bi-moment distribution characteristics were identified between the two ship types, revealing that the superstructure (i.e., island layout, referred to as "island" hereafter) significantly influences the bi-moment distribution. With torque and the bending-torsion characteristic coefficient selected as governing parameters, regression analyses were conducted to establish longitudinal bi-moment distribution formulas for single-island and double-island container ships, yielding two sets of concise regression formulas. These formulas can be applied to the global bending-torsion strength assessment and the torsional ultimate strength evaluation incorporating warping stress in the preliminary design stage of container ships.