A decade ago, the technology of strengthening structures using FRP composites was primitive, with very few publications. Nowadays, the potential growth of research is achieved to the wide recognition of the importance of this new technology. In fact, significant practical applications have been preceded and the development of design methods have been achieved. However, the specific design methods for each applications are still lack of design skills in spite of the wide applications of FRP composites in the construction industry. The purpose of this paper is to report the development of design methods for FRP-strengthened structures by technical review design methods and guidelines of fiber reinforced composites.