Abstract: Pitting corrosion is a common damage affecting the residual strength of offshore structures, whose deterioration mechanisms are not yet clear. In this study, a meso-scale corrosive pit model with cylindrically uniformly distributed pits on the surface of a pipe shell was adopted. The model was integrated into a macro-scale structure with pitting wastage damage. After studying key factors of mixed dimensional finite element model including the description method of the pits in the macro-scale structures, the partition principle of the structural multi-scale regions, the connection technique for the across-scale interface of the multi-scale region, and the nonlinear solution technique for the multi-scale model, a numerical approach addressing multi-scale modelling of offshore structures with pitting corrosion were proposed. Results of an aging offshore structure showed that the proposed multi-scale model can be successfully used to bridge the description gap between the meso-scale damage and the macro-scale structure. In addition, based on such multi-scale finite element models, the rule of the deterioration caused by corrosive pitting to the residual strength was remarkably reflected, providing a practical method for the evaluation of residual strength of offshore structures in engineering practice.