Abstract:  This paper aims at the development of a unified-integrated software system for the engineering design of offshore spar platforms, which can implement the chain-work, i.e., hull design, analysis, and code verification. By means of computer aided engineering (CAE), the chain-work of the engineering design of offshore platforms can be automatically carried out. Then, based on the integrated software system, the global strength of a truss spar platform is analyzed. The analysis involves parametric finite element modeling, mapping of hydrodynamic loads to structural models, finite element analysis, yielding strength verification, and buckling calculation and verification. The results indicate that the most dangerous part of a truss spar platform under the condition of operation load cases comes from the intersections of hard tank-truss and soft tank-truss.