This paper explains the development of a knowledge-based expert system for the optimal strength design of composite structures subjected to various loading conditions and design heuristics constraints. The optimal stacking sequences are obtained by integration of a knowledge-based expert system, genetic algorithm and finite element analysis. Because this expert system in optimal stacking sequence design adopts a finite element method as an analysis tool, it isn``t limited to laminate design but can be applied to a general composite structure. The optimal stacking sequence combination is drawn from the discrete ply angles and design heuristics stored in the knowledge for the given application of interest. Results of this study were verified through comparison with quasi-isotropic lay-ups.