This paper presents the investigated resuts of numerical simulation pertaining to the hull girder strength of container ships in irregular sea. Using the so-called total system of hull girder strength analysis developed by the authors, the analysis of the long-term prediction of structural response of three container ships is carried out. And the wave-induced stresses in longitudinal strength members, distortion of hatch openings and the torsional deformation of hull girder are studied from the point of view of the long-term prediction. As a result of this simulation, the following conclusions are obtained. (1) In the middle part of ship, the wave-induced normal stress in the upper deck at the side edge of hatch opening is in the stress range of 89.5kg/mm² and the wave-induced shearing stress in the outer hull at the load water line is below 10kg/mm² with probability level 10^-6. The normal stress of outer hull at the bilge part is in the same level with that of the upper deck. (2) In the fore hold structure, the normal stress of the upper deck is almost in the same level with that of the middle part of ship. Furthermore the torsional deformation of hull girder is considerably large compared with that of the middle part of hull because of the decrease in the torsional rigidities. (3) As to the distortion of hatch openings, the elongation Δ l of the diagonal length of them is largest in the hatch of the middle part, but there are small differences in the ratio Δ l / l with same probability level.